Current results have Democrats controlling 222 seats to the Republicans' 196, with 17 contests still undeclared, according to the Associated Press.
Four tight races in California are still counting ballots and could go either way.
"It's a huge moment and victory for the president", Press Secretary Sarah Huckabee Sanders told reporters at the White House Tuesday night.
The bottom line is that Trump is facing a new and formidable apparatus of accountability - and even he knows how badly this could end for him.
They want to find out what Trump said to Russian President Vladimir Putin at a July meeting in Helsinki unattended by any White House aides.
The political and practical stakes were sky-high.
Some Democrats have already vowed to force the release of his tax returns. In the 115th Congress, the Republicans controlled the House 235 to 193 and the Senate 51 to 47 with 2 Independents (both of whom caucus with the Left).
For the past two years, Republicans have subjected Trump to relatively little oversight, spurning most requests from the minority party.
Pelosi spoke with Trump and McConnell after the Democrats' victory. The Senate was always an uphill battle for Democrats, who needed to defend 26 of the 35 seats in play, compared to just 9 for the Republicans. The GOP's grip on high-profile governorships in Florida, Georgia and Wisconsin were at risk as well. Trump would merely need to defend them, fold them into the White House's message, and convince voters they were an administration priority.
McConnell eschewed further attempts to get him to respond to heated presidential rhetoric, refusing to call the migrant caravan - still hundreds of miles from the southern USA border - a "crisis", as Trump did in high profile campaign rallies created to turn out the GOP base.
"Many Democrats support the president's trade agenda", lamented Dieter Kempf, the head of the Federation of German Industries, the main business lobby group in Germany, a leading exporter.
Exit Polls Show Trump A Major Factor In 2018 Midterm Election Voting
Trump, whose approval ratings are mired in the low 40s, has vowed to his supporters at every rally they will "win, win, win". The second time was following 9/11 in 2002, when Republicans gained eight House and two Senate seats under President Bush.
Tanzanian authorities detain media activists - CPJ
They were released on Thursday morning but are yet to get their passports back. CPJ's executive director Joel Simon has called for their immediate release.
Prince Harry Discusses The Moment His Dad Saved The Royal Wedding
Meghan cried, I'm sure, she did cry, and they both said, 'Take care of yourself, we are really anxious about you, '" he said on ITV's " Good Morning Britain " in June.
The news is not all good for Trumpism. The Justice Department dropped the charges after his trial ended in an hung jury.
Pennsylvania was particularly daunting for Republicans after court-imposed redistricting and a rash of retirements put several seats in play.
In south Florida, former Health and Human Services Secretary Donna Shalala defeated Republican Maria Elvira Salazar.
And in the aftermath of Tuesday's midterm elections, the Republican Party is increasingly exclusively the party of Trump. Rep. Conor Lamb, D-Pa., was re-elected to the House.
In the Senate, only a third of the total 100 seats were up for reelection, with 35 spaces for new Senators. The basic premise is that when government is unified, members of Congress are more likely to vote with the president rather than adhere to its constitutional role of checking presidential power. He and the first lady were to host an evening watch party for family and friends.
House Democrats will formally nominate their candidate for speaker after Thanksgiving.
Republicans must also loudly promote their success with two of the country's most enduring, important issues: the economy and national security. Democrats are relying more upon women, people of colour, young people and college graduates.
Most worryingly of all, the voters they motivate seem impervious to recognizing - or simply do not care about - the broader threat to American values and democracy that the Republican party of today represents. A margin of less than half a percentage point automatically triggers a recount.
The demographic divides were coloring the political landscape in different ways.
Pelosi, who held the position from 2007-2011, is widely considered to be the front-runner to retake the speaker's office, but a handful of House Democrats called for new leadership prior to the election.
House Democratic Leader Nancy Pelosi wouldn't answer a question Wednesday about whether Democrats will seek Trump's tax filings. Democratic Senate incumbents were up for re-election, for example, in North Dakota, Indiana, and Missouri - states Trump carried by nearly 25 percentage points on average two years ago.
The most likely impact of House investigations would be a swarm of legal issues for the White House, which is likely to fire up Trump's base for 2020 while producing no results to satisfy Democrat voters.
Voters in Minnesota and MI elected the first two Muslim women to serve in the U.S. Congress: Ilhan Omar, a former refugee who fled Somalia's civil war, and Rashida Tlaib, a Detroit-born Palestinian-American.
As of early Wednesday, voters were on track to send at least 99 women to the House, surpassing the previous record of 84.