Millions of Americans are voting in the midterm elections on Tuesday, with Republicans excited about the prospect of winning back Congress.
If they do so, it could be harder for President Joe Biden to pass laws compared to now, with a Democrat-controlled White House.
The balance of political power in the US will be dictated by whether Democrats or Republians win the US House of Representatives, about a third of the Senate and key state governorships.
Mr Biden rallied voters in Maryland and Republican ex-President Donald Trump did the same in Ohio, on the eve before voting.
In the first national election since the January 6, 2021 Capitol riot, the Democrats have tried to focus key races on fundamental questions about the nation’s political values.
Democrats argue that Republican victories could profoundly reshape the country, such as by eliminating abortion rights nationwide and threatening American democracy.
But Republicans say the public is tired of Biden policies amid high inflation and fears about crime.
“We know in our bones that our democracy is at risk,” Mr Biden said during an evening rally in Maryland, where Democrats have one of their best opportunities to reclaim a Republican-held governor’s seat.
“I want you to know, we’ll meet this moment.”
Arriving back at the White House a short time later, Mr Biden was franker, saying: “I think we’ll win the Senate. I think the House is tougher.”
Mr Biden won Maryland with more than 65 per cent of the vote in 2020 and appeared with Wes Moore, the 44-year-old Rhodes Scholar who could become the state’s first Black governor.
The president said at an earlier virtual event: “Imagine what we can do in a second term if we maintain control.”
Mr Trump was in Ohio for his final rally of the 2022 campaign - and already thinking about his own future in 2024.
He had teased that he might formally launch a third presidential run and has promised a “big announcement” next week at his Mar-a-Lago estate in Florida.
“If you want to stop the destruction of our country and save the American dream, then tomorrow you must vote Republican in a giant red wave that we’ve all been hearing about,” Mr Trump said at Monday night’s rally.
He also went after House Speaker Nancy Pelosi, saying “I think she’s an animal” mere days after her husband, Paul, was severely beaten by an attacker at the couple’s San Francisco home.
While the GOP likes its chances of flipping the House, control of the Senate could come down to a handful of crucial races. Those include Georgia, Arizona and Pennsylvania, where Democratic Governor John Fetterman was locked in a close race against Republican celebrity surgeon Mehmet Oz.
Elon Musk, whose purchase of Twitter has roiled the social media world, used that platform on Monday to endorse the GOP, writing: “I recommend voting for a Republican Congress, given that the Presidency is Democratic.”
That came too late for more than 41 million Americans who had already cast early ballots.