The Democrats on Wednesday secured a majority in the House of Representatives for the first time in eight years but the Republicans retained control of the Senate in US midterm elections seen as a referendum on the Trump presidency.
According to projections based on exit polls, having snatched at least 23 seats from Republicans, the Democrats were set to retake control of the House, splitting control of bicameral Congress with the Republicans, reports Xinhua news agency and Efe news.
With swathes of congressional districts still waiting for voting results, it remained unclear how many seats the Democrats will eventually end up with in the next Congress.
The Democratic Party's success has been widely anticipated by pre-voting polls though suspense remains as to how strong a "blue wave" is sweeping across the US.
Democrats captured 13 Republican-held seats early, ejecting incumbents in the suburbs of Kansas City, Philadelphia, Pittsburgh, Minneapolis, Miami and Washington D.C
The Party also managed to win a number of gubernatorial races, including in the states of Illinois, New Mexico and Kansas, balancing out the Republicans who controlled 33 governorships prior to the election.
All 50 states and Washington D.C. went to the polls on Tuesday as Republicans and Democrats battle for control of the two houses of Congress, with experts saying that voter turnout could be the highest for a midterm election in 50 years, CNN reported.
Americans voted for all 435 seats in the House of Representatives and 35 of 100 seats in the Senate - the two bodies that make up Congress. Governors are also being chosen in 36 out of 50 states.
By winning the House, Democrats will gain a powerful new pedestal to investigate President Donald Trump's administration, his personal finances, and the hotels, golf courses and other businesses he still owns.
They were also likely to press for details about the 2016 election, asking whether Trump or his campaign colluded with the Russian government's efforts to sow misinformation and pro-Trump messages.
But the Republicans snuffed out Democrats' hopes of winning the Senate.
Projections have indicated that the Republicans were to gain at least three seats to increase their majority to a minimum of 51-42 per cent with 94 per cent of seats declared, Efe news reported.
Although it was not yet possible to confirm the number of seats the Republicans will count from next January when the new Congress takes office, the projections confirm the surveys of the past months, which pointed to a conservative majority in the Upper House.
The first big victory of the night for Republicans in the Senate was that of Mike Braun, who won the seat of the Senate for Indiana, which had been in the hands of Democrat Joe Donnelly.
Texas Republican Ted Cruz, who was challenged in the last few months by Democrat Beto O'Rourke, managed to keep his seat, although by a narrower margin than the conservatives ever have historically recorded in the Lone Star state.