Pelosi's return to the speakership is likely but not assured, as some of the House candidates running in Trump-won districts tried to distance themselves from her leadership.
Fox News declared at 9:45 p.m. that Democrats had gained at least 23 seats in the lower chamber, giving Democrats control of the House for the first time since 2010.
It was the first national election in the United States since the 2016 race in which Russian Federation interfered, according to USA intelligence agencies, with a campaign of hacking and propaganda to sow discord, harm the Democratic presidential candidate and boost Mr Trump's chances.
With memories still fresh from 2016, when Trump astonished experts by defeating the heavily favoured Hillary Clinton, pollsters are being cautious.
In recent days, Mr Trump has accused Democrats of being "radical socialists who want to model America's economy after Venezuela", and said they wanted to invite "caravan after caravan of illegal aliens into our country".
U.S. intelligence agencies have concluded the Russian government meddled in the 2016 election with social media posts meant to spread misinformation and sow discord, an accusation denied by Moscow.
"We'll strive for bipartisanship, seeking common ground as we are responsible to do".
The party in the White House often loses seats after a president's first two years in office, even if the president isn't a controversial figure like Trump.
But the Democrats' push into President Trump country remained uncertain. The current session comprises 235 Republicans, 193 Democrats and seven vacant seats (five of which were last held by Republicans). Women hold 84 out of 435 House seats, a record number.
Kentucky, meanwhile, will give us an early indication of how the US House races are shaping up.More news: Kemp turns election system worries into a political weapon
Some of the biggest Democratic stars of the campaign lost.
In gubernatorial races, Republican Kris Kobach, a Trump ally, was beaten by a Democrat in Kansas.
History was in the making in several states, as Michigan Democrat Rashida Tlaib became the first Muslim woman elected to Congress and Democrat Ayanna Pressley became the first black woman elected to the House from MA.
A loss of the House will also trigger significant second guessing of the President's tactics, given that he chose not to make the booming economy his primary midterm argument, instead turning to a searing indictment of Democrats focusing on immigration and laden with racial language. First, potential voters favor Democrats by 8-9pp in socalled generic ballot polls.
Trump is under 50% approval in Texas, where Sen.
The President planned to have dinner with his family and to watch the results, which could have a profound impact on the rest of his term and could reshape Washington's balance of power, in the residence of the White House.
"This is basically, we are judging the Republican Party for the last two years". But it's also possible that Democrats will falter.
Voting in Chicago, James Gerlock, 27, a Republican, said he wanted to see more of the soaring economic growth that Trump says is the fruit of his business-friendly policies.
Democrats have so far managed to win a net of 13 seats, many of which run though suburban areas.
He noted that Republicans now hold 33 governorships, compared to 17 for the Democrats.
"I think everyone was bracing for any possible, insane scenario to show itself tonight but it basically looks like the baseline consensus forecast was correct", said Michael Purves, Head Of Equity Derivatives Strategy At Weeden & Co, New York.