(CNN) Three presidents -- one sitting and two former -- descended on Pennsylvania Saturday for a final-stretch midterm push that underscored the stakes of one of the nation's most closely watched Senate races.
For President Joe Biden, who held a rare joint appearance with former President Barack Obama in Philadelphia to boost the Democratic candidate Lt. Gov. John Fetterman, Pennsylvania amounted to a political stress test in his home state, where he's traveled 20 times since taking office.
For former President Donald Trump, who rallied Saturday night outside of Pittsburgh in the city of Latrobe, a win by his hand-selected candidate Dr. Mehmet Oz could prove his own enduring viability in a commonwealth he lost by a narrow margin in 2020.
The consequences extend well beyond next week's election. As Trump prepares to announce a third presidential bid, potentially in the coming weeks, Biden's aides are taking their own initial steps toward mounting a reelection campaign. For a several-hour stretch on Saturday, the dynamics of a potential 2020 rematch were laid bare.
The moment marks a historic anomaly. Former presidents have typically only waded sparingly into daily politics, mostly avoiding direct criticism of the men occupying the office they once held. Not since Grover Cleveland in 1892 has a defeated one-term president returned to win the White House again.
The convergence of presidents in Pennsylvania, each warning of dire consequences should the opposing party prevail, reflected the altered norms Trump precipitated when he took office nearly six years ago, quickly issuing false accusations against Obama of spying and general malfeasance.
In North Philadelphia, Biden told a packed crowd at Temple University that Fetterman would protect Social Security and Medicare and would look out for veterans.
"My objective when I ran for president, was to build an economy from the bottom up and the middle out. It's a fundamental shift, compared to the Oz and the mega MAGA Republican trickledown economics," Biden said, referring to Fetterman's GOP opponent, Dr. Mehmet Oz.
As the crowd booed, the president continued, "No really. This ain't your father's Republican Party. This is a different breed of cat. I really mean it. Look, they're all about the wealthier getting wealthy. And the wealthier staying wealthy. The middle class gets stiffed. The poor get poorer under their policy."
Obama offered a prebuttal to the possibility of Democratic losses.
"I can tell you from experience that midterms matter, a lot," Obama said, a reference to the 2010 election that saw the GOP retake power in the House of Representatives during his first administration.
"When I was president, I got my butt whupped in midterm elections. I was elected in the midst of a financial crisis and we did the right things to get the economy back on track but it was slow and people were frustrated, just like they are right now."
Biden, who spent much of his first year in office trying to avoid saying Trump's name, is no longer so cautious. He called out "Trump and all his Trumpies" at a rally in California this week and identified Florida Gov. Ron DeSantis as "Trump incarnate" during a fundraiser outside Fort Lauderdale on Tuesday. At his own rallies, Trump plays a video reel of slip-ups to cast his successor as a gaffe-prone senior citizen -- though he hasn't as frequently gone after Obama.
Obama, meanwhile, has issued his harshest criticism to the cast of candidates backed by Trump, many of whom deny the 2020 election results and have modeled themselves after the 45th president.
"It doesn't just work out just because somebody's been on TV. Turns out, being president or governor is about more than snappy lines and good lighting," Obama said in Arizona last week of the Republican gubernatorial candidate Kari Lake, a former local news anchor.
Pennsylvania's senate and gubernatorial contests are the sole marquee races of this year's midterm cycle Biden has stumped in repeatedly. In other high-profile races, candidates have maintained their distance from a president with underwater approval ratings.
That hasn't been true of Obama, who has been in high demand among Democrats in close races. In the final weeks of the campaign, Obama has held raucous rallies in Georgia, Michigan, Wisconsin, Arizona and Nevada -- all states Biden has avoided in the last several months as candidates work to stave off Republican momentum.
That's a 180-degree turn from midterm cycles during Obama's presidency, when it was Biden venturing to more states -- including conservative-leaning districts -- where the sitting president was considered a drag on Democratic candidates.
Biden is hardly irritated or even surprised that Obama is more of a draw on the campaign trail this year than him, according to officials. He has discussed some of the races with his former boss and believes Obama's message is both resonating with voters and complementary to his own.
Still, their joint appearance Saturday only served to underscore their divergent styles and political abilities -- a comparison even some Democrats say ultimately favors Obama.
"I know you always ask me how we're doing. We're going to win this time around I think. I feel really good about our chances," Biden told reporters Friday in California.
The president has been bullish on Democrats' chances next week, even as many Democrats grow increasingly anxious about their party's prospects. His campaign schedule -- in blue states stumping for candidates in closer-than-expected races -- is itself a signal of Democrats'' vulnerabilities.
In the final days of the campaign, Biden has been traveling mostly to blue states he won, but where Democrats are nonetheless running closer-than-expected races. He stopped in New Mexico, California and Illinois before stumping in Pennsylvania on Saturday, and will campaign with the embattled New York Gov. Kathy Hochul on Sunday. He'll spend Election Eve in Maryland.
People familiar with Biden's thinking say he accepts that not every Democratic candidate will welcome him as a surrogate while his approval ratings remain underwater. And he has told fellow Democrats he respects their political intuition when it comes to their own races.
But he has grown frustrated at coverage suggesting he is political albatross, according to people familiar with the conversations, arguing his policies -- when properly explained -- are widely popular with voters.
Compared to both Obama and Trump, Biden has held far fewer campaign rallies for his party during this midterm cycle. Most of his engagements over the past month have been official events, delivered to crowds that sometimes only number a few dozen.
His rallies have begun drawing larger crowds in the waning days of the campaign. Six hundred people had to be turned away from an event in Southern California on Friday, according to the White House. And Biden addressed an overflow crowd in New Mexico that couldn't fit inside the main venue when he was holding a rally with Gov. Michelle Lujan Grisham.
"I know you don't think it, but I think we have pretty good crowds. They're fairly enthusiastic. You don't write it that way, but they are," Biden said as he was departing California on Friday.
Still, his events haven't generated the same electricity as Obama's. The former president has laid into Trump and his acolytes who are running for office during his string of rallies across the country over the past weeks, using stinging humor and an air of bemusement to ridicule Republicans.
Like Biden, he's also argued the American system of government is at stake in next week's election, telling a crowd in Arizona that "democracy as we know it" could perish if election deniers take office.
Obama and Biden last appeared together at the White House in September, when Obama's official portrait was unveiled in the White House East Room. The event had been put off while Trump was in office, partly because neither the Obamas nor the Trumps were interested in putting on a show of friendship.
As he campaigns for his endorsed candidates this fall, Trump has made little attempt to conceal his larger intentions: to buttress his own likely presidential campaign he hopes will return him to the White House.
"Get ready, that's all I'm saying," Trump told a crowd in Sioux City, Iowa, on Thursday, adding that he "will very, very probably do it again."
Top Trump aides have discussed the third week of November as an ideal launch point for his 2024 presidential campaign if Republicans fare well in the midterm elections, sources familiar with the matter said.
For Biden, the decision may take a little longer. He has pointed to family discussions around the holidays when asked about his own timeline. Members of his political team have made early preparations for a campaign infrastructure, operating under the assumption he will decide to run again.
His motivating factor, aides say: Whether Trump jumps in himself.
This story has been updated with additional details.