WASHINGTON — Republicans are eyeing major gains in Tuesday’s elections and appealing to supporters over the final weekend of the 2022 campaign to sideline Democrats. President Joe Biden and his two most recent Democratic predecessors said the prospect of GOP victories could undermine the future of American democracy.

More than 39 million people have already voted early or by mail in an election that will decide control of Congress and key governorships.

Biden was set to campaign in suburban New York on Sunday after former Presidents Barack Obama and Bill Clinton made closing cases to voters on Saturday.

Former President Donald Trump, who planned a Miami rally later Sunday, hopes a strong GOP showing on Election Day will generate momentum for the 2024 run that he is expected to launch in the days or weeks after polls close.

Not invited to his Florida event is the state’s Republican governor, Ron DeSantis, who is running for reelection against Democrat Charlie Crist and is widely considered Trump’s most formidable challenger if he also were to get into the White House race.

In Pennsylvania on Saturday night, Trump said he hoped the GOP would have “an historic victory” in the midterms. But DeSantis also was on his mind — he referred to the governor as “Ron DeSanctimonious.” It’s a rivalry that’s been simmering for more than a year as DeSantis has taken increasingly bold steps to boost his national profile and build a deep fundraising network.

DeSantis, who became a popular national figure among conservatives during the pandemic as he pushed back on COVID-19 restrictions, shares Trump’s pugilistic instincts. By most measures, Trump remains easily the most popular figure in the Republican Party. But many Trump supporters are eager for the prospect that DeSantis might run, seeing him as a natural successor to Trump, without Trump’s considerable political negatives.

Trump has privately groused about DeSantis for failing to say definitively that he will sit out the race.

When Joe O’Dea, the GOP candidate for Senate in Colorado, said he would prefer someone other than Trump as the 2024 nominee and cited DeSantis and others. Trump slammed O’Dea candidate on social media: “MAGA doesn’t Vote for stupid people with big mouths,” Trump said, referring to his “Make America Great” campaign slogan.

Days later, DeSantis endorsed O’Dea, who had twice voted for Trump.

DeSantis held a rally Saturday night near St. Petersburg and stuck mostly to his record as governor.

For national Democrats, the focus is on the fate of their narrow majorities in the House and Senate.

Voters may punish the party controlling the White House and Congress amid surging inflation, concerns about crime and pessimism about the direction of the country. History suggests the party in power will suffer significant losses in the midterms.

Trump’s weekend travels were part of a late blitz that will also take him to Ohio, where his endorsed Senate candidate, JD Vance, is running against Democrat Tim Ryan.

Trump has long falsely claimed he lost the 2020 election only because Democrats cheated and has even begun raising the possibility of election fraud this year. Federal intelligence agencies have warned of the possibility of political violence from far-right extremists in the coming days.

Biden’s pitch to voters centers on championing his administration’s major legislative achievements, while warning that abortion rights, voting rights, Social Security and Medicare are at risk should Republicans take control of Congress.

Obama, who joined Biden in Philadelphia on Saturday, noted that generations of Americans died for democracy and said, “You can’t take it for granted.” And Biden said: “We have to reaffirm the values that have long defined us.”

At a New York rally for Gov. Kathy Hochul, who is in a tight battle for reelection, Clinton said the loss of House and Senate control by Democrats would have “enormous consequences.”

“It’s going to be hard, it’s going to be tough but we aren’t giving up hope,” said Lee Saunders, president of the American Federation of State, County, and Municipal Employees, the nation’s largest union of public employees with 1.4 million members.

“Clearly people are concerned about the economy,” he said. But voters also are “concerned about the freedoms being taken away from them, whether you’re talking about voting rights or whether your talking about a women’s right to choose.”