Washington (AFP) - Republicans and Democrats traded final blows Monday ahead of midterm elections that could upend Joe Biden's presidency, weaken Western support for Ukraine and even open the door to a comeback bid by Donald Trump.
More than 40 million ballots have been cast through early voting options, meaning the outcome was already taking shape before polls open nationwide Tuesday.
Biden acknowledged that Democrats face an uphill battle to retain control of Congress, telling supporters that "if we're able to hold on, we're going to be in an incredible shape."
"I know that sounds like a very high expectation," he admitted, adding that "we're up against some of the darkest forces we've ever seen in our history."
Biden, who has framed his closing argument as a warning that American democracy is on the line, was set to close out days of campaigning for Democratic candidates at a rally Monday evening near Baltimore.
Lame duck?
Trump -- using the midterms to repeatedly tease a possible 2024 White House run, even as he faces criminal probes over taking secret documents and trying to overturn the 2020 election -- was holding a rally in Ohio.
With polls showing Republicans in line to seize the House of Representatives, the increasingly far-right party eyed snarling the rest of Biden's first term in aggressive investigations and opposition to spending plans.
Kevin McCarthy, who would likely become speaker of the House -- placing him second in line to the president -- refused to rule out impeachment proceedings.
"We will never use impeachment for political purposes," McCarthy told CNN."That doesn't mean if something rises to the occasion, it would not be used at any other time."
One key question remained whether the US Senate would also flip, leaving Biden as little more than a lame duck.
With Congress out of Democrats' hands, Biden would see his legislative agenda collapse.
That would raise questions over everything from climate crisis policies, which the president will be laying out at the COP27 conference in Egypt this week, to Ukraine, where Republicans are reluctant to maintain the current rate of US financial and military support.
While insisting he supports Ukraine's struggle, McCarthy told CNN there could be no "blank check" -- a nod to the isolationist Trump wing of his party and a signal likely sending shivers through Kyiv.
Adding to tensions -- and a reminder of Moscow's murky role throughout Trump-era US politics -- Kremlin-connected oligarch Yevgeny Prigozhin boasted that Russia was trying to tilt the outcome.
White House Press Secretary Karine Jean-Pierre, however, dismissed Prigozhin's statement as "not surprising," while also reassuring voters that law enforcement has not identified any "specific, credible threats" to election security from domestic sources.
Jean-Pierre also expressed confidence that US support for Ukraine "will be unflinching and will be unwavering" -- even if Republicans win midterm elections.
Just how badly Tuesday goes will also likely determine whether Biden, who turns 80 this month and is the oldest president ever, will seek a second term or step aside, plunging his party into fresh uncertainty.
'Wake-up call'
Up for grabs are all 435 House seats, a third of the 100 Senate seats, and a slew of state-level posts.
Popular former president Barack Obama and other Democratic stars have been racing from campaign to campaign in hopes of seeing off the predicted Republican "red wave."
But the political landscape has been tilting away from Democrats since the summer, as Republican messaging about high inflation, crime and illegal immigration overwhelmed the incumbents.
The Senate is more of a toss-up but Democratic hopes of keeping the upper chamber, which they currently only barely control thanks to the tiebreaking vote from Vice President Kamala Harris, look fragile.
Dave Wasserman of the nonpartisan Cook Political Report told MSNBC there could be a Republican gain of 15-25 House seats, while "Republicans might gain the one seat they need to win control of the Senate."
Races in Pennsylvania, Nevada, Arizona, Georgia, Wisconsin, New Hampshire and Ohio have narrowed to projected photo finishes, and any one of them could swing the balance of power.
Democrats have focused their closing arguments on voting rights, protecting abortion access and welfare -- and on the threat posed by growing support among Trump Republicans for political conspiracy theories.
Republicans counter that a vote for Democrats means more soaring inflation and crime.
In a typically attention-grabbing move, billionaire Elon Musk used his newly purchased Twitter social media site to endorse a Republican takeover of Congress.
"Shared power curbs the worst excesses of both parties," the world's richest person tweeted to his 114 million followers."Therefore I recommend voting for a Republican Congress, given that the Presidency is Democratic."
