Americans will vote on Tuesday in the crucial midterm election that could decide the political future of President Joe Biden and his predecessor Donald Trump – who has all but announced he will seek the White House again in 2024.

Biden’s Democrats face a gargantuan battle to hold on to Congress after a race the president has described as a “defining” moment for US democracy – while Trump’s Republicans have fought hard on issues like inflation and crime.

Trump — heavily hinting at a new run — seized the spotlight on election night to make “a big announcement” a week from now, on Nov. 15, while Biden made a final appeal for Democrats to turn to the polls en masse participate .

“The power is in your hands,” Biden said at a rally near the capital. “We know in our bones that our democracy is in jeopardy and we know this is your moment to defend it.”

As polls show Republicans are poised to take the House of Representatives, the increasingly far-right party has spent the remainder of Biden’s first term aggressively investigating and opposing spending plans.

Returning to the White House on Monday night, Biden told reporters he believed Democrats would win the Senate — although he conceded “it’s going to be difficult” to keep the House and that his life in Washington could get “more difficult.”

If both the House and Senate topple, Biden would be little more than a lame duck.

With Congress out of the hands of the Democrats, he would see his legislative agenda crumble.

That would raise questions about everything from the climate crisis policies that the President will lay out at this week’s COP27 conference in Egypt; to Ukraine, where Republicans are reluctant to maintain current levels of US financial and military support.

An influx of far-right Trump supporters in Congress would also hasten the shift that is taking place within the Republican Party since the former real estate tycoon stunned the world by beating Hillary Clinton for the presidency in 2016.

Despite criminal investigations into stealing top-secret White House documents and attempting to overturn the 2020 election, Trump has used the midterm elections to cement his status as the de facto Republican leader and presumptive presidential nominee.

In a typically dark, rambling speech to fans in Dayton, Ohio, Trump said, “If you support the decline and demise of America, then you must, you must vote for the far left, crazy people.”

“If you want to stop the destruction of our country, tomorrow you have to vote Republican in a huge red wave,” he said — before teasing his 2024 announcement.

Across the country, voters urged their fellow citizens to cast their ballots in midterm elections, which historically have had low turnout.

“I would stress, choose, choose, choose,” 24-year-old college student Luke Osuagwu told AFP in Atlanta, Georgia.

“If you don’t vote, you can’t really represent society or anything like that,” agreed Alethia McClenton, a 45-year-old Georgia Aquarium staffer. “It’s very important that everyone does their part.”

More than 40 million ballots were cast through early voting options, meaning the result was beginning to take shape before Election Day.

Polling stations on the East Coast will start at 6am (1100GMT) and close 12 hours later.

Up for grabs are all 435 seats in the House of Representatives, a third of the 100 Senate seats, and a slew of state-level posts. Four states are also holding referendums on abortion – California, Vermont, Kentucky and Michigan.

Senate races in Pennsylvania, Nevada, Arizona, Georgia, Wisconsin, New Hampshire and Ohio have narrowed to projected photo finishes, and any of them could shift the balance of power.

However, the final results may not be known until days – or even weeks in some cases – after Election Day, setting the stage for promising challenges.

Trump has already unsubstantiated claims that the swing state of Pennsylvania “rigged” the midterm elections — repeating his 2020 election playbook, which he falsely claimed was stolen by Biden.

Citing growing support for conspiracy theories among Trump and Republican voters and their push to restrict access to abortion, Biden warned that democracy and fundamental rights are at stake on Tuesday.

Republicans have countered that voting for the Democrats means rising inflation and violent crime, and are trying to turn the midterm elections into a presidential referendum.

The result will likely determine whether Biden, who turns 80 this month and is the oldest president ever, seeks a second term in 2024 — or resigns.