The Democrats seized control of the House in Tuesdays' pivotal midterm elections.
Control of the lower chamber will allow Democrats to block key parts of President Trump's agenda and re-open investigations into his administration.
The Democrats elected are also younger, more racially diverse and include more women.
A Democrat-led House presents obstacles to the Trump administration, which has taken a hardline stance on immigration in particular.
But despite the apparent setback, President Trump responded with a celebratory tweet, calling it a “tremendous success" after the Republicans retained control of the Senate.
The likely new House speaker, Democrat Nancy Pelosi, a veteran progressive from San Francisco who's held the post before, also made clear that the new majority would exert an institutional check on the White House.
"Today is more than about Democrats and Republicans. It is about restoring the Constitution's checks and balances to the Trump administration."
Democrats could pick up more than 30 seats in the House, but they lost significantly in the Senate races in major red states like Indiana, North Dakota and Tennessee.
Republican businessman Mike Braun also beat the Democratic incumbent Joe Donnelly in the battleground state of Indiana where Trump won by 20 percentage points back in 2016.
When it comes to Democrats, the two African-American Democratic governor candidates Stacey Abrams in Georgia and Andrew Gillum in Florida lost to their Republican challengers.
And a rising star Beto O'Rouke was defeated in his race against Republican Senator Ted Cruz of Texas.
But the Democrats were successful in attracting an army of young voters, compared to the last midterms four years ago.
Cha Sang-mi, Arirang News.