However, thunderstorms are forecast for Tuesday along the eastern coast, as well as snowstorms in the Midwest, which could affect turnout. Trump, the GOP's chief messenger, warned that significant Democratic victories would trigger devastating consequences. This victory marks a significant blow to Trump as the Democrats are now in a position to challenge the U.S. president's policy agenda. He added: "The Democrat agenda is a socialist nightmare". "It's an awakening of the Democratic Party".
But it remains to be seen whether Democrats' rage will amount to the so-called "blue wave" they have anticipated for almost two years, or whether it's even enough to gain the 23 seats needed to eke out a Democratic majority in the House. And they would claim subpoena power to investigate Trump's personal and professional shortcomings. Liberal House member Beto O'Rourke's underdog Senate campaign fell short in conservative Texas against Republican incumbent Ted Cruz. The infamous excitement that we saw among people throughout 2016 is the same energy that has been seen across the country at rallies leading up to today's midterm elections.
Long lines and malfunctioning machines marred the first hours of voting in some precincts, including in Georgia, where some voters reported waiting up to three hours to vote in a hotly contested gubernatorial election.
Trump's Republican coalition is increasingly older, whiter, more male and less likely to have a college degree.
Democrats boast record diversity on the ballot.
But in both chambers, the sheer number of airtight toss-up races means there are no guarantees about tonight's outcome, even as generic congressional ballots show Democrats with the advantage over Republicans and the party of the president historically loses seats in their first midterm elections.
Despite the shocking news that the Rasmussen Reports Generic Congressional Ballot on Monday rated Republicans leading with "likely midterm voters" for the first time by 46 percent to the Democrats' 45 percent, California's Democrat House delegation is busy jockeying to gain powerful leadership positions if the Democrats flip House control.
"We have a choice to make tomorrow morning: Are we going to wake up and bask in sorrow and defeat?" Control of the U.S. House will depend on the effectiveness of the spillover from the President's message to suburban women voters in districts where he did not campaign. The demographic shifts also reflect each party's closing argument.
"Everything we have achieved is at stake", Trump declared in his final day of campaigning. He dispatched more than 5,000 troops to the region, suggesting soldiers would use lethal force against migrants who throw rocks, before later reversing himself. Still, Republican voters tended to be overwhelmingly supportive of the president.
But former President Barack Obama was among those who directly targeted Trump and his personal style and beliefs, saying at one point "the character of the country is on the ballot".
As the returns came in, the House was on track to break the record of 84 female members of one party or the other.
Trump's polarizing impact on the country has driven unusually high interest in the election, the first major political test of his presidency and one that will provide Democrats with clues to the strategy they'll need to challenge him in 2020.
The Republican grip on high-profile governorships in Florida, Georgia and Wisconsin were at risk as well.
Trump was spending Election Day at the White House and tweeting support for Republicans in the toughest races.
"I have worked at this poll the last three elections and this is the biggest turnout ever", said Bev Heidgerken, 67, a volunteer at a polling place in Davenport, Iowa.
"I think it will actually be an advantage to Trump is they pursue impeachment".
He noted that creating civil rights for Americans, better health care and workers' wages - and also preventing them from being rolled back happens with actions at the polls.
On Tuesday night, he called to congratulate Pelosi and acknowledged her plea for bipartisanship, the leader's spokesman said. "That's why our economy is growing like it is". "They ignored the party bosses who said they should wait their turn". All 435 seats are being contested today.
They face a far more hard challenge in the Senate, where they are nearly exclusively on defense in rural states where Trump remains popular.
In a sign that Trump dominance two years ago isn't necessarily fatal for Democrats, their incumbents were expected to win re-election in six other states that he carried.
Republicans retained Senate seats in the South, Midwest and West and ensured at least a 51-49 majority, equal to their current margin.
Given Trump's stunning victory in 2016, few were confident in their predictions. "I think it's about the character of the country", he said in Wilmington, Delaware, where he voted.