(CNN) Democrats in crucial Senate races across the country are swamping the airwaves with ads in the furious battle for control of the chamber, far outpacing Republican spending as their party grows more bullish about their prospects for retaking the majority.
In battleground states nationwide, Democratic candidates and outside groups have been inundating the air with ads, promoting their records, seeking to distinguish themselves during their own competitive primaries and bashing the GOP senators whose seats they seek to occupy.
In 12 races that will determine the next Senate majority, Democrats have spent roughly $30 million more on the airwaves than their Republican counterparts, according to a CNN review of data from Kantar's Campaign Media Analysis. In total, Democrats -- including campaigns and outside groups -- have spent $109 million on television, radio and digital advertisements, compared with $79 million for Republicans since the beginning of the election cycle last year, the records show.
While some of the disparity is due to Democrats attacking each other during the party's primaries, both sides are keenly aware that Republicans have been outspent on the airwaves so far. Top Republicans expect the gap to close as the elections draw nearer.
"Our mission is to hold a Republican Senate firewall no matter what else happens," said Steven Law, the president of the Senate Leadership Fund, the super PAC aligned with Senate Majority Leader Mitch McConnell and a major spender on the GOP side.
"We are seeing another 'green wave' of Democrat cash flooding into Senate races -- just like in the last three elections. That's why we carefully conserve our resources while Democrats have already spent tens of millions dragging clunker candidates through primaries."
Yet Republicans are alarmed at the surge of cash flowing to Senate Democratic campaigns, particularly as President Donald Trump's standing has deteriorated amid his handling of the coronavirus crisis and race relations in the United States. Some strategists are warning that Democratic Sen. Chuck Schumer of New York could become the majority leader if the trend continues.
"These Dem challenger numbers are staggering," Scott Reed, the senior political strategist at the US Chamber of Commerce, emailed CNN. "Folks better get ready to watch Schumer roll back all of the regulatory, tax and judicial progress of the last 3 years if he becomes the Senate Leader."
"The entire business community and America's job creators will all be on the Schumer menu next year," he added.
To take back the Senate, Democrats need to pick up only three seats if former Vice President Joe Biden wins the presidency, since the vice president breaks a tie in the chamber. They need a net pickup of four seats if Trump is reelected. The Democrats have competitive bids for at least nine seats in eight states -- North Carolina, Colorado, Maine, Montana, Georgia, Kansas, Iowa and Arizona -- while they are playing defense in just two states, Alabama and Michigan. Georgia has two Republican senators up for election this year, Kelly Loeffler and David Perdue.
Schumer, exuding his party's growing confidence, told CNN last month: "We will win the Senate."
Television spending appears to have had an impact in some of the races. In Iowa, GOP Sen. Joni Ernst found herself down 3 points in a Des Moines Register poll last month after her Democratic opponent, Theresa Greenfield, benefited from big spending ahead of the primary. To date this cycle, the GOP has been outspent by $10 million in advertising in that race, including the candidate campaigns and outside groups, according to the CNN review.
In Maine, Republican Sen. Susan Collins is facing the toughest reelection since winning her seat in 1996, as Democrats have so far outspent her party by more than $6 million in a state that Hillary Clinton carried four years ago.
In North Carolina, Cal Cunningham is neck-and-neck with Republican Sen. Thom Tillis, with a recent New York Times-Siena College poll showing the Democratic challenger up 3 points in the race, within the survey's margin of error. Cunningham, too, benefited from a surge of advertising to help him win his primary. His party has spent more than $5 million in the state, compared with the more than $3.6 million spent by the Republicans.
The National Republican Senatorial Campaign, which is advertising earlier than it has in past election cycles, released its first ad in North Carolina last weekend, seeking to link Cunningham to prominent liberals like Sen. Bernie Sanders of Vermont and Rep. Alexandria Ocasio-Cortez of New York.
The pattern is evident across the country. In Michigan, where Democratic Sen. Gary Peters is fending off a bid from John James, a businessman and Army veteran, the Democrats have advertised more than $4 million than the Republicans have so far. In Arizona, Democrats supporting retired NASA astronaut Mark Kelly have spent nearly $3 million more in ads than Republicans backing Sen. Martha McSally. And in Montana, Democrats have spent over $1 million more on behalf of Gov. Steve Bullock than Republicans have on behalf of Sen. Steve Daines.
Some of the numbers reflect fiercely competitive primaries. In Kentucky, where former fighter pilot Amy McGrath fended off a tough bid from state Rep. Charles Booker, Democrats have already spent roughly $10 million more than McConnell and his allies. In Colorado, Democrats spent over $6 million more than the Republicans, as former Gov. John Hickenlooper stumbled but then soundly defeated former state House Speaker Andrew Romanoff.
But in Georgia, one of the few states where the Republicans have spent more than the Democrats -- by nearly $10 million -- the state is in the throes of a special election that includes Loeffler and Republican Rep. Doug Collins.
Democrats have also been outspent in Alabama and Kansas by several million dollars where there are also hard-fought GOP primaries.
Unlike fellow Democrats, Sen. Doug Jones of Alabama, one of the most vulnerable senators this cycle, has not been the beneficiary of outside spending from national groups. Jones has $8 million in his campaign war chest, compared with about $1 million combined for the two Republicans hoping to take him on, former Attorney General Jeff Sessions and former Auburn football coach Tommy Tuberville, according to the latest Federal Election Commission filings.
Jones told CNN recently that he's not concerned by the lack of help from outside groups.
"I've got my race," Jones said. "I feel pretty good about where we are. I don't worry about any of that one way or the other. It's still early."