Initial exit poll results are in and they are looking very bad for President Trump and his party.
Louisiana Rep. Steve Scalise, the No. 3 House Republican leader, told NPR that fewer GOP members overall means "you don't have as many people that can just be free agents".
But what if that doesn't happen?
Democratic candidates for the House of Representative have raised $649m (£500m) from individual donors, more than doubling the $312m tally for the Republicans. It reports that failure in the midterms could plunge the Democrats into an "utter and complete psychological meltdown".
There is no contingency plan.
The predictive model at FiveThirtyEight now projects an 88 per cent chance of them winning the seats required. A CNN poll released on November 5 found that Democrats led Republicans on a generic ballot by 13 points, 55 percent to 42 percent.
While Trump is not on the ballot, the most polarizing U.S. president for decades has put himself at the center of every issue. So to the extent that the polls were wrong in 2016, polling models have been corrected. It all depends on how accurately they have predicted voter turnout.
Early voting leading up to Tuesday's midterm election revealed a wide variety of concerns with voting and registration systems around the country - from machines that changed voter selections to registration forms tossed out because of clerical errors.
Races to watch include Democrat Beto O'Rourke's challenge to Senator Ted Cruz in traditionally deep-Republican Texas. The other, Ileana Ros-Lehtinen of Florida, is retiring (and a third represents Puerto Rico but does not a vote). In the last such congressional elections in 2014, there were 27.5 million early votes.
Among white college-educated women, Democrats enjoy a 28-point advantage: 61 per cent to 33 per cent. "They have to go out there to get a following".
The hyper-charged environment is expected to drive record turnout in some places, but on the eve of the election, it's far from certain which side will show up in the greatest numbers.
Democrats during the 2016 demanded Trump release his tax returns.
What if their nightmare comes true again?
The party hopes younger voters, suburban moderates and minorities will be drawn to the polls to react against the president's rhetoric. Republicans now hold 51 against the Democrats' 49 (with two independents).
Whatever the outcome, Trump made clear he knew his political future was on the line.
"That's an invasion. I don't care what they say", Trump said to cheers. "We are the Democratic Party", he said. Former President Barack Obama was in his words "shellacked" in 2010 and went on to win re-election in 2012.
Republicans are counting on Trump to rally his supporters in the closing hours to help maintain their narrow 51-to-49 seat edge in the Senate. He can't remember ever voting for a Democrat but said he might this time in protest.
Many people have already voted. In a White House speech, the president said he would sign an order preventing border-crossers from claiming asylum, a legally questionable proposition, and said he'd told military troops he's mobilising to the border to respond to thrown rocks like they were "rifles".
Democrats were most optimistic about the House, a sprawling battlefield set largely in America's suburbs where more educated and affluent voters in both parties have soured on Trump's turbulent presidency, despite the strength of the national economy.
"If you look back through the last 50 or 60 years of USA history, if you are an incumbent President, the chances are you will be re-elected and there is a strong pattern of the United States two terms for one party, two terms for the other". If Trump runs for re-election, someone else will have to lead the charge against him. "No one, as we saw with Hillary Clinton, has got the same appeal to the coalition that he put together". Other 2020 prospects on the ballot included Massachusetts Sen.
If the party descends into chaos, one of them will have to emerge as its new leader.