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The US Capitol in Washington, DC, is seen on October 25, 2024.
CNN  — 

Entering Election Day on Tuesday, the battle for control of the US House of Representatives rests on a knife’s edge, with a historically small universe of competitive races poised to determine the chamber’s majority in the next Congress – an outcome that could have far-reaching consequences for the next president’s agenda.

All 435 House seats are on the ballot, with Republicans defending a slim majority and Democrats needing a net gain of four seats to flip control of the chamber. There is a clear consensus among both parties that whichever side emerges with a majority is likely to have little room to spare. A single-seat majority is not outside the realm of possibility. That could pose a challenge for Mike Johnson, if the GOP retains control and restores the Louisiana Republican as House speaker, or Hakeem Jeffries, if Democrats retake the chamber and make history by installing the New York Democrat as the first Black speaker.

If Donald Trump is returned to the White House, a Republican House could help advance his agenda while a Democratic-controlled chamber would serve as a potential roadblock, particularly if the GOP is able to flip the Senate, as it appears poised to do given a favorable map. As for Kamala Harris, she could be the first newly elected Democratic president in more than a century to start her term without concurring House and Senate majorities, though controlling at least one chamber could give her some much-needed leverage in negotiations.

One clear sign of how consequential control of the chamber is to both parties: More than $1 billion has been spent on advertising in House races just since Labor Day, with Democrats accounting for more than 57% of that total, according to data from AdImpact.

With so much at stake, CNN has identified 10 races to watch on Tuesday – grouped into buckets that nod to broader themes across the House landscape. This is far from an exhaustive list, but the selected contests could offer some clues about how the fight for control of the chamber may ultimately be settled.

Virginia’s 7th District: The early indicator

Inside Elections rating: Tilt Democratic

This open-seat contest between Democrat Eugene Vindman and Republican Derrick Anderson will be one of the most closely watched races early in the night Tuesday.

Democratic Rep. Abigail Spanberger decided against seeking a fourth term, instead launching a campaign for governor in 2025. The district, which stretches from the Washington suburbs to the rolling hills of the commonwealth’s Piedmont region, would have backed Biden under the current lines by about 7 points in 2020.

Vindman and Anderson are both Army veterans and lawyers. In 2019, Vindman found himself at the center of Trump’s first impeachment when the then-ethics lawyer for the National Security Council and his twin brother, Alexander – a director on the NSC – sounded the alarm about a phone call between the president and his Ukrainian counterpart, Volodymyr Zelensky.

The other Virginia race to watch is the coastal 2nd District, anchored by Virginia Beach, where GOP Rep. Jen Kiggans is facing off against fellow Navy veteran Missy Cotter Smasal. If either party were to capture both races, that could foreshadow a favorable environment.

Nebraska’s 2nd District: The Biden crossover seat

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Nebraska Rep. Don Bacon, left, and Democratic challenger Tony Vargas.

Inside Elections rating: Tilt Democratic

The number of crossover districts – seats represented by members of one party but carried by the president of a different party – has been on the decline in recent years. Entering Tuesday’s elections, there are 21 such districts, not counting a handful of Southern seats that saw their lines redrawn after the 2022 midterms.

Sixteen are Republican-held seats that Joe Biden would have won four years ago. One of them is the Omaha-area seat that belongs to GOP Rep. Don Bacon, a centrist retired Air Force officer who has been a top target for Democrats ever since he flipped the district in 2016, defeating Rep. Brad Ashford by a little more than a percentage point.

He faces a rematch with Democrat Tony Vargas, a 40-year-old state senator vying to be Nebraska’s first Latino member of Congress. In 2022, Bacon defeated Vargas by less than 3 points.

While the district known as Nebraska’s “blue dot” appears to be leaning toward Harris in the race for Electoral College votes, the contest at the House level looks more competitive. That means to survive his latest challenge, Bacon will likely need to draw a decent slice of support from Harris voters to punch his ticket back to Capitol Hill for a fifth term.

Maine’s 2nd District: The Trump crossover seat

Inside Elections rating: Toss-up

On the flip side, there are five seats currently represented by Democratic members of Congress that Trump would have carried during the 2020 election.

Democratic Rep. Jared Golden has crafted a moderate profile by challenging his party on issues ranging from spending to immigration. The tattooed 42-year-old Marine Corps veteran has distanced himself from Harris, declining to endorse the Democratic nominee, an acknowledgement that he will need to appeal to Trump voters in a district the GOP nominee would have won by 6 points four years ago and is favored to carry again.

Golden’s opponent is the Trump-endorsed Austin Theriault, a 30-year-old state representative and former NASCAR driver, who Republicans hope will be able to appeal across the massive, mostly rural district, which stretches from rocky shorelines in the south all the way north to the state’s border with Canada.

Gun control has emerged as a key issue in the race after Golden reversed his opposition to an assault weapons ban following the 2023 mass shooting in Lewiston – the district’s biggest city – that killed 18 people. Theriault has accused his Democratic rival of having “flip-flopped on the Second Amendment.”

Another potential wild card is Maine’s use of ranked-choice voting, which could come into play if neither candidate receives a majority of votes on Election Day with an independent candidate running a write-in campaign.

More than $34 million has been poured into the race since early September, with Democrats outpacing Republicans by nearly $3 million, according to data from AdImpact.

Michigan’s 7th District: Open-seat opportunity

Inside Elections rating: Tilt Republican

Democratic Rep. Elissa Slotkin’s decision to run for the US Senate in Michigan opened up this Lansing-based seat as a prime pickup opportunity for Republicans in a district Biden would have carried by less than a point in 2020.

The race between Democrat Curtis Hertel and Republican Tom Barrett – two former state senators – has drawn nearly $37 million in ad spending since early September, the second most of any House race in the country, according to AdImpact data.

Barrett, a retired Army helicopter pilot, ran against Slotkin in 2022, losing to the well-known and well-financed incumbent by more than 5 points. While Hertel offers a different resume than Slotkin, a former CIA officer, he has ties to Gretchen Whitmer, Michigan’s popular Democratic governor, and comes from a family with political roots in the state.

The neighboring 8th district, where longtime Democratic Rep. Dan Kildee is retiring, is another open-seat target for Republicans, with the party eyeing both Central Michigan races as opportunities to possibly expand its slim majority or offset losses by GOP incumbents elsewhere on the map.

Colorado’s 8th District: The freshmen

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Colorado Rep. Yadira Caraveo and Republican challenger Gabe Evans participate in a debate in Denver on October 8, 2024.

Inside Elections rating: Toss-up

Both parties have vulnerable freshman members running for the first time in a presidential cycle, bringing a fresh set of dynamics from the 2022 midterms with a more intense mix of national political crosscurrents.

Democratic Rep. Yadira Caraveo, a pediatrician and former state legislator, won a newly created seat in the northern suburbs and exurbs of Denver after Colorado gained a seat following the once-in-a-decade census count – becoming the first Latina elected to Congress from the state. This year she faces a challenge from GOP state Rep. Gabe Evans, a fellow Mexican American and a former Army helicopter pilot and police officer.

Immigration and border security have been front and center in this race, with Trump shining a national spotlight on the Denver suburb of Aurora in the neighboring 6th District during a recent visit, where Evans also spoke. The 8th District, where nearly 40% of the residents are Latino, could be a place where Trump’s gains with that group of voters might have some down-ballot impact.

In a sign of its competitiveness, nearly $32 million has been poured into the race since early September, with Democrats outpacing Republicans by $6 million.

Pennsylvania’s 10th District: Too much MAGA?

Inside Elections rating: Tilt Republican

GOP Rep. Scott Perry has not shied away from controversy during his six terms in the US House, including his support for Trump’s efforts to overturn the 2020 election results, which led to the FBI seizing the congressman’s cell phone.

Even as the former chair of the House Freedom Caucus embraces his firebrand status, he has managed to fend off Democratic challengers with relative ease, winning his most recent race in 2022 by nearly 8 points despite the swirl of scrutiny around his actions.

That strategy is facing its toughest test this year in the form of a challenge from Democrat Janelle Stelson, a political newcomer but familiar face to many Central Pennsylvania residents. Stelson spent decades as a news anchor and reporter in the region and is now trying to turn onetime viewers into voters. Democrats see Stelson’s profile, combined with her prolific fundraising and the changing politics of the district – Trump would have won it by 4 points in 2020, but Democrat Josh Shapiro carried it by a double digits during his 2022 run for governor – as signs that Perry is potentially vulnerable. Stelson also scored the endorsement of five former GOP members of Congress who served with Perry as she seeks to appeal to moderate voters.

Both parties have ramped up their spending here in the final weeks, signaling a tight race that could offer a glimpse about the level of support for MAGA-aligned candidates in districts that appear to be trending toward the political middle.

New York’s 19th District: Empire State of mind

Inside Elections rating: Tilt Democratic

The lackluster showing by Democrats in New York during the 2022 midterm elections cost the party any chance it had at keeping control of the House. Democrats are hoping the state will lay the groundwork this year for the party’s return to the majority.

Thanks in part to a slightly more favorable map after state lawmakers approved new lines, Democrats are looking to pick up at least two seats in the Empire State, with the potential for more.

A top target is the 19th District, which stretches from the Hudson Valley to the Finger Lakes. It’s currently represented by GOP Rep. Marc Molinaro, who won the seat by less than 2 points in 2022 and faces a rematch with Democrat Josh Riley, a lawyer who served as counsel to former. Sen. Al Franken on the Senate Judiciary Committee.

The contest has seen the most spending of any House race over the past two months – $38.5 million – with Democrats outspending Republicans by more than $5 million. The presidential race is also poised to play a factor in the 19th District, where voters would have backed Biden by more than 4 points in 2020. But Republicans also believe that Trump is running stronger in blue states than he did four years ago.

California’s 45th District: California, here we come

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California Rep. Michelle Steel and Democratic challenger Derek Tran.

Inside Elections rating: Toss-up

The other big prize on Tuesday is California, which is home to at least a half dozen highly competitive races, four of them GOP-held seats that Biden would have carried with relative ease in 2020 and another he would have lost by only a single point.

Harris’ ascension to the top of the Democratic ticket could give her party a home-state boost, though Republicans, as noted above, see Trump improving his standing in states such as California and New York, which are not competitive at the presidential level despite the former president’s pronouncements to the contrary.

One of the best barometers of the political environment in California is the 45th District, based in Orange and Los Angeles counties, with a constituency that is nearly 40% Asian American and more than 30% Latino. The seat is currently held by GOP Rep. Michelle Steel, a Korean immigrant first elected in 2020, who is facing off against Democrat Derek Tran, a US Army veteran and first-generation Vietnamese American.

Orange County has signaled the political shifts of the Trump era, with Democrats making gains there during the 2018 midterms but losing ground two years later as the GOP clawed back House seats despite the president’s loss.

Another point to keep in mind: If the majority comes down to California, the country could be waiting a while as the state takes time to count ballots.

North Carolina’s 1st District: The redistricting reshuffle

Inside Elections rating: Tilt Democratic

Redistricting in three Southern states is set to provide House Republicans a small dose of relief heading into Election Day. The GOP is poised to pick up three seats thanks to a new map in North Carolina, while fresh lines in Louisiana and Alabama are expected to deliver Democrats a pair of seats – effectively giving Republicans one more seat to start the evening.

There is a fourth seat in North Carolina – the 1st District in the northeast corner of the state, bordering Virginia – that became more favorable for Republicans under the redrawn lines, going from one that Biden would have carried by nearly 7 points in 2020 to one with a margin of victory of less than 2 points. That has Republicans sensing an opportunity to unseat first-term Democratic Rep. Don Davis, an Air Force veteran who won his 2022 race under the old lines by a little less than 5 points.

Davis’ opponent is Laurie Buckhout, a retired Army colonel and political newcomer. Both candidates have aligned themselves with the nominees of their parties, appearing at campaign events with them in the Tar Heel State, though Davis’ endorsement of Harris in July came a day after he voted for a GOP resolution that criticized the vice president over her handling of the southern border.

Iowa’s 3rd District: Stopping the suburban slide

Inside Elections rating: Tilt Republican

Since Trump’s emergence as the leader of the GOP almost a decade ago, the suburbs have been sliding away from Republicans. One of the key questions animating the 2024 election is whether that erosion has stopped – or at the very least been slowed. The answer could be a determining factor in several House races, where Republican incumbents are hoping to avoid headwinds stirred by the former president among suburban voters.

Iowa’s 3rd District – home to Des Moines and its suburbs – is one place to keep an eye on for signs of how Trump is faring and the potential impact on down-ballot contests. In 2016, Trump won Dallas County, west of Des Moines, by nearly 10 points. His margin there shrunk to just 2 points against Biden.

GOP Rep. Zach Nunn, an Air Force officer, was first elected in 2022 – defeating Democratic Rep. Cindy Axne by about 2,000 votes. He’s running against Lanon Baccam, the son of refugees from Laos who is also a combat veteran and former official in the US Department of Agriculture.

If Harris can expand the Democratic Party’s sway in the suburbs, this is a “reach” seat that could be in play for the party on Tuesday.

CNN’s David Wright, Matt Holt, Molly English, Renée Rigdon and Andrew Menezes contributed to this report.