Faced with the possibility of keeping the Senate but losing the House, aides have begun laying out the political reality to Trump, who could face an onslaught of Democratic-run investigations and paralysis of his policy agenda. With 218 seats needed for a majority, Democrats have won 219 and the Republicans 193, with winners undetermined in 23 races.
The president bet big on a xenophobic closing message, warning of an immigrant "invasion" that promised to spread violent crime and drugs across the nation. Both Barack Obama's and Bill Clinton's numbers were 5 points higher, and both suffered major midterm losses of 63 and 54 House seats respectively.
On Sunday Trump and former U.S. president Barack Obama made dueling election appearances, offering sharply different views on the country's problems but agreeing on the high stakes for voters in the final 48 hours of a tight campaign.
Mr Trump has dropped hints that the Democrats could take the House, saying a number of times that there were too many candidates for him to campaign with personally - a possible excuse if things do not go his way.
Turnout was expected to be much higher than in previous times on Election Day Tuesday when US voters headed to the polls to choose their representatives in both chambers of Congress in the midterm elections.
"It's all fragile", he said on the call.
In Indiana, Republican Mike Braun knocked off Democratic Sen.More news: In France, under the rubble found the bodies of the dead
The elections will mark the first nationwide vote since Russian Federation targeted state election systems in the 2016 U.S. presidential race but federal, state and local officials have sought to reassure the public that their voting systems are secure.
At the same time, Democrats re-elected embattled New Jersey Sen.
How close are the elections going to be? Dean Heller, the only Republican seeking re-election in a state Democrat Hillary Clinton won in the 2016 presidential race.
Vermont independent Sen. Bernie Sanders and Democrats Elizabeth Warren of Massachusetts, Kirsten Gillibrand of NY and Minnesota's Amy Klobuchar were easily re-elected.
Trump spent Tuesday at the White House, tweeting, making calls, monitoring the races and meeting with his political team.
He and the first lady were to host an evening watch party for family and friends. Democrats are also interested in Trump's tax returns, which he has declined to make public. Others have pledged to pursue impeachment, although removal from office is unlikely so long as the GOP controls the Senate or even maintains a healthy minority.
Sanders, the independent who has always been one of the state's most popular politicians, spent little time campaigning ahead of Tuesday's election.More news: 2-month-old Boeing plane crashed in Indonesia after key sensor replaced
Trump's racially tinged anti-immigrant appeals could hurt Republican candidates in swing states like Arizona and Nevada where college-educated voters could be decisive, but his rhetoric could help in deeply conservative areas. AP VoteCast also showed a majority of voters considered Trump a factor in their votes. Like other Democrats across the country, Spanberger emphasized protecting people with pre-existing conditions from being denied coverage or charged more by insurers.
In suburban areas where key House races will be decided, voters skewed significantly toward Democrats by a almost 10-point margin.
"The only check right now on the behavior of these Republicans is you and your vote", Obama told supporters in Gary, Indiana, during a rally for endangered Democratic Senator Joe Donnelly.
Democrats faced a far more hard challenge in the Senate, where they were nearly exclusively on defense in rural states where Trump remains popular.
The White House for days has stressed the historical headwinds it faced: In the last three decades, 2002 was the only midterm election when the party holding the White House gained Senate seats.
Tuesday's contest saw several historic firsts in the Democratic camp: in Kansas Sharice Davids - an attorney and former mixed martial arts fighter - became the first Native American woman elected to Congress.
But most Democratic legislative candidates focused on "bread-and-butter issues", Hortman said in a recent interview.More news: Lionel Messi trained by himself a day after Inter 1-1 Barcelona
"Things are pretty good, yet we have all this division and we have this president who's relatively unpopular, so we have this unusual juxtaposition", said Kent State politics professor Michael Ensley, citing Trump's poor approval ratings despite a rollicking USA economy and the absence of any major foreign-policy challenges.