The Democrats picked up the 23 seats they would need to take from the GOP, and were expected to meet the 218 total needed to take control though more races were still undecided. Several television networks, including the president's favorite Fox News Channel, yanked a Trump campaign advertisement off the air on the eve of the election, determining that its portrayal of a murderous immigrant went too far.
With a House majority, Democrats will have the power to investigate Mr Trump's tax returns, possible business conflicts of interest and allegations involving his 2016 campaign's links to Russian Federation.
That was a risky strategy with a potentially huge reward: had Republicans held on to both chambers of Congress, Trump would have been able to tout another major upset victory. We are going to see a Democratic majority (in the House) that is going to do everything it can to hold the Trump administration's feet to the fire and use subpoena power to do so.
And Rep. Adam Schiff, slated to become chairman of the House Intelligence Committee, has vowed to probe alleged Trump campaign-Russia collusion.
Democrats faced a far more hard challenge in the Senate, where they were nearly exclusively on defence in rural states where Mr Trump remains popular. Since 1946, the president's party has lost an average of 25 House seats in midterm elections, according to Gallup.
Control of the House gives Democrats the ability to launch investigations into the president and stifle his agenda.
Alongside all 435 House seats and a third of the Senate on the ballot on Tuesday were 36 gubernatorial races.
In the Senate, where Democrats were defending seats in 10 states that Trump won, Republicans ousted four Democratic incumbents.
In the Senate, Republican Mike Braun captured incumbent Joe Donnelly's seat in IN, and Republican Kevin Cramer beat incumbent Democratic Senator Heidi Heitkamp in North Dakota, marking disappointment for the Democrats.
White House Spreads Doctored Video To Justify Temper Tantrum Against CNN Reporter
Mr Acosta is seen trying to keep hold of the microphone while Trump's aide makes three unsuccessful attempts to take it from him. The adjustment is "too precise to be an accident", said Shapiro, who trains instructors to use video editing software.
Some of the biggest Democratic stars of the campaign season were struggling.
Republican Rep. Ron DeSantis defeated Democratic Rep. Andrew Gillum in the Florida governor's race by one point.
Democrats did succeed in holding on to Sen. Democratic Senator Sherrod Brown was projected to hold his seat in Ohio.
Democrats also captured governorships in Michigan, Illinois and Kansas.
"I think that's 100 percent due to the president's leadership and the success he has had in the first two years since taking office", said Sanders.
In other notable contests, Democrat Alexandria Ocasio-Cortez won her race for a House seat in NY - becoming, at 29, the youngest woman ever elected to Congress.
What's happening in House races?
Democrats turned out to register disapproval of Trump's divisive rhetoric and policies on such issues as immigration and his travel ban targeting several Muslim-majority countries. Democrats are relying more upon women, people of color, young people and college graduates.
The greatest hopes - and worst fears - of both main political parties in the U.S. went unfulfilled in the midterm elections on Tuesday, as the Democrats were projected to wrest a majority in the House of Representatives away from the Republicans, but at the same time will lose Senate seats.
The governor focused much of his campaign on his opposition to President Donald Trump and Trump's policies, and he continued that in his victory speech, at times addressing the president directly, saying NY is not "buying" what Trump is selling.