Democrats need a net gain of 23 seats to win the House for the first time since the Tea Party wave of 2010, and the latest polls give them a good chance to do so.
But he conceded on Monday the House may slip from his party's grasp.
The Democrats achieved a supermajority in the House when Rachel Prusak, a nurse, beat Republican Rep. Julie Parrish to represent a district south of Portland.
The president will then stand trial in the Senate, where a two-thirds vote is necessary for removal - a milestone that is unprecedented in American history.
Pennsylvania was particularly daunting for Republicans after court-imposed redistricting and a rash of retirements put several seats in play. That is the question confronting several GOP incumbents, including New Jersey Rep. Leonard Lance.
As for Republicans retaining control of the Senate, she called it "a huge moment and victory for the president".
The incumbent Democratic Senator Joe Donnelly is under pressure from his Republican challenger Mike Braun.
Fifty-eight of voters said the country is headed in the wrong direction, compared with 41 percent who said it is on the right track, according to a nationwide survey conducted in all 50 states for The Associated Press and Fox News.
Democrats Joe Manchin in West Virginia and Tammy Baldwin in Wisconsin won their Senate re-election bids, both states Trump won in 2016.
In northern Virginia, Republican incumbent Barbara Comstock lost to Democrat Jennifer Wexton, while in one surprise win, Democrat Max Rose - a former boxer who raised millions on the strength of a viral video - unseated Rep. Dan Donovan, R-N.Y., in a seat encompassing Staten Island and Queens. Four years later, Brat could find himself on the losing end of another upset, facing a strong challenge from Abigail Spanberger, a former Central Intelligence Agency operations officer.
Voters "rejected the politics of hate, the politics of division and the politics of ideology", Spanberger told supporters Tuesday night. Still, while Bill Clinton and the Democrats lost 54 seats to Republicans in 1994, and Barack Obama and the Democrats lost 63 seats to the Republicans in 2010, it doesn't look like Donald Trump and the Republicans will lose almost that many seats to Democrats in these 2018 midterms.
Romney clinched the win Tuesday as he defeated Democrat Jenny Wilson, a member of the Salt Lake County council. The race was considered a toss-up.
The most recent record in voter turnout during congressional midterm elections, when the White House was not on the line, came in 1982, when 49 percent of the voting-age population showed up to vote, according to the US Census Bureau.
"This was a hard campaign", Curbelo told reporters in Miami.
While at his polling place Tuesday, Bredesen said it was an important day that is not just about a Democrat and a Republican but about two different visions for the job.
In a disappointment for the Democrats, incumbent GOP Rep. Garland "Andy" Barr held off a strong challenge from Democrat Amy McGrath, a former fighter pilot.
There's been a lot of attention paid to the 25 GOP seats Clinton carried in 2016 - and rightfully so - but Democrats are also on offense in numerous dozen districts that swung from Barack Obama in 2012 to Trump four years later.
Yet Democrats' dreams of the Senate majority as part of a "blue wave" were shattered after losses in Indiana, Tennessee, North Dakota and Texas.
Donald Trump faces greater restraints on his presidency after Democrats won control of the US House of Representatives and pledged to hold the Republican accountable after a tumultuous two years in the White House. As that number indicates, voter enthusiasm is high. It was just the second midterm election in over three decades when the party holding the White House gained seats.
Preliminary exit poll data found that Trump was a factor for nearly two-thirds of House voters.
Problems with voting machines were preventing some Americans from casting ballots in a dozen states, USA rights advocates said, following complaints about registration problems, faulty equipment and intimidation they had received throughout early balloting. Still, Republican voters tended to be overwhelmingly supportive of the president.
A inquiry into the Russian Federation investigation, led by special counsel Robert Mueller, could be ordered by the House Judiciary Committee to determine if "impeachable" offences were committed by Trump, he said.
Investors often favour Washington gridlock because it preserves the status quo and reduces uncertainty, even though many investors this time around had been hoping for a continuation of the Republican agenda.
Health care has been the dominant message for Democrats this cycle - mentioned in more than half the party's TV ads.
"They could be tempted to say that the public wants an impeachment process based on uncertain claims, but I don't think the public wants that", the professor at University of Toronto said.
Despite positive feelings about the economy, overall, voters were pessimistic about the direction of the country.