With control of Congress, statehouses and the president's agenda at stake, some of the nation's top elections were too close to call.
But Republicans appeared bound to hold onto the Senate, and possibly even pick up a couple of seats.
All 435 seats in the US House were up for re-election, although fewer than 90 were considered competitive while Some 35 Senate seats were in play, as were nearly 40 governorships and the balance of power in virtually every state legislature.
The airtight House contests are scattered across the country: Among them, Democrat Abigail Spanberger is challenging Republican Rep. Dave Brat in Virginia's 7th Congressional District; Democrat Danny O'Connor and Republican Troy Balderson are rematching in Ohio's 12th Congressional District; and Democrat Harley Rouda is challenging longtime Rep. Dana Rohrabacher in California's 48th Congressional District. The second time was following 9/11 in 2002, when Republicans gained eight House and two Senate seats under President Bush. He faces a well-funded challenge from Democrat Tom Malinowski, a former State Department official, in a district Hillary Clinton carried by a single point.
Democrats hoped their supporters' would surge to the polls.
Trump said in an interview with Sinclair Broadcasting on Monday that he wished he had a softer tone during his first two years in office - even as he kept up his attacks on political rivals.Trump blamed the political vitriol on election season.
Early indications would appear to support this.
The president so dominates politics across the country that despite not being on any ballot he has made the election largely about him.
Some 38.4 million Americans have cast their ballots in early voting compared to 27.4 million in the 2014 midterms, according to the US Elections Project.
"I think, like the TV stations have been saying, it's a referendum on the Trump presidency", said Eloisa Alvarez as she voted in Miami.
Trump has used what many say is divisive and xenophobic rhetoric in the lead-up to Tuesday's vote.
"Trump is improving the economy - that's the most important thing for me", Rivera said. "I just love the deregulation and I just want to keep everything moving, because I'm loving it".
Trump himself noted the energy as he wrapped up a punishing schedule of rallies around the country that were meant to boost Republican candidates - and his own brand heading towards reelection in 2020. He once hosted a campaign rally at a Vegas gun store. An open seat that included Atlantic City was also ripe for Democratic pickup by state lawmaker Jeff Van Drew after the GOP campaign committee abandoned Republican Seth Grossman over racially charged comments. "No one from outside can stir paranoia or fear that can change that".
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If Republicans lose a lot of seats this time around, it will be perceived as a pushback from the American people against Trump's agenda.
A CNN/SSRS poll released Monday showed Democrats with a gaping 55% to 42% lead over Republicans among likely voters in a generic congressional ballot.
The outcome of the midterms will also mark the culmination of a bitter partisan battle for control of Congress and set the stage for the 2020 elections, where an expansive field of Democratic presidential candidates is expected to challenge Trump after his first term in office. The GOP will fall short of the 60 votes needed to break Democratic filibusters, procedural delays that kill legislation.
The first signs will come from key congressional races on the east coast in suburban Virginia, New Jersey, Florida and NY, however this will likely be a long day.
"Maybe you get a ripple, but I certainly don't think that there's a blue wave", she told reporters, pointing to several early Republican wins. So, just like in 2016, what many said could not be done could be done once again today.
"Tomorrow will be a new day in America", said House Minority Leader Nancy Pelosi, who's in line to become the next House speaker should Democrats take the majority.
Women also contested governor's races across the country.
For Democrats, the road to the 218-seat majority ran through the two dozen suburban districts Clinton won and through swaths of Trump country in the Rust Belt and heartland where voters backed the president two years ago.
Election workers assist would-be voters at First Ward Creative Arts Academy on November 6, 2018, in Charlotte, North Carolina. "So I understand that you can have both sides", Gonzalez said.
Carol Reynolds, 83, described herself as a former Republican as she cast her ballot in Laguna Beach.
Trump, whose approval ratings are mired in the low 40s, has vowed to his supporters at every rally they will "win, win, win". It would be the first time the party has controlled the House since 2010.
Polls are also closed in parts of in, where Democrat Joe Donnelly, a top target of the President's frenetic final midterm election campaign swing, is fighting an uphill battle for re-election against Republican Mike Braun.