Tuesday's vote was seen as a referendum on a polarising president, even though he is not up for re-election till 2020.
Democrats won the majority of New York's state Senate seats on Tuesday, taking hold of the legislative body for the first time in years.
The Democrats can now launch investigations into Mr Trump's administration and business affairs, from tax returns to potential conflicts of interest, while blocking his legislative agenda.
The party were most optimistic about the House, a sprawling battlefield set largely in America's suburbs where more educated and affluent voters in both parties have soured on Mr Trump's turbulent presidency, despite the strength of the national economy.
While Deb Haaland in New Mexico and Sharice Davids in Kansas are the first two Native American women in Congress.
While Republican Ted Cruz was re-elected to Senate in Texas, Rashida Tlaib and Ilhan Omar became the first two Muslim women to be elected to the US Congress.
What's happening in Senate races?
The tax law has been particularly problematic for Republicans in New Jersey, where four of five GOP-held seats were being seriously contested.
In the Senate, centrist Democrats from states that Trump won In 2016 such as Joe Donnelly In IN and Heidi Heitkamp In North Dakota were replaced by conservative Republicans who may credit their victories to the president.
The US President who headlined an unprecedented 50 rallies - 30 in the last two months alone - and has campaigned for dozens of candidates at all levels of government, according to White House Press Secretary Sarah Sanders, watched the results come in with friends and family in the White House residence.
The loss of power will test Trump's political hold on House Republicans, most of whom had pledged their support for him lest they face the wrath of the party's core supporters, who remain in his corner.
Russian Fighter Intercepts US Spy Plane
While the USA military said that their aircraft had acted in accordance with global law and did not provoke "Russian activities". Near the city of Sevastopol, seat of the Russian fleet of the Black Sea, the aircraft approached 35 kilometers to the coast.
It's a tale of two chambers.
In the Texas Senate, where there's no prospect of a Democratic takeover, Democrats on Tuesday celebrated Nathan Johnson's defeat of Huffines and Beverly Powell's defeat of Konni Burton. Donald Trump will continue to have a Republican majority ready and willing to confirm his executive and judicial appointments.
"I am very, very, very concerned about the Republican Party and the direction it has taken", said Pfradt, who said she used to be a Republican but now identifies as an independent".
In the House of Representatives, however, the story is different.
Democrats knocked off at least 17 GOP incumbents, picking up moderate, suburban districts across the country. Democrat Monica Duran lead Republican Arthur Erwin, 62.42 percent to 37.58 percent in District 24, while Democrats Kerry Tipper lead Republican Kristina Joy Alley 57.76 percent to 39.56 percent in District 28.
And outside Richmond, Virginia, one-time tea party favorite Rep. Dave Brat lost to Democrat Abigail Spanberger, a former Central Intelligence Agency operative motivated to run for office after the GOP vote to gut the Affordable Care Act.
The early wins give Democrats a share of the seats they'll need for House control. That leaves a shrunken core dominated by conservatives from rural areas whose constituents overwhelmingly support Trump.
Trump had fought hard before polling day, crisscrossing the country to claim that Democrats would introduce socialism and making incendiary attacks on illegal immigration that opponents denounced as racist.
Republican Brian Kemp is well ahead of Democrat Stacey Abrams in Georgia's governor election.
The night's news wasn't completely disastrous for Democrats.
Republican Rep. Ron DeSantis defeated Democratic Rep. Andrew Gillum in the Florida governor's race by one point.