The Democrats have taken control of the US House of Representatives in the mid-term elections, dealing a blow to President Donald Trump.
A Democratic majority in the lower chamber for the first time in eight years will restrict his ability to steer his programme through Congress.
But Mr Trump's Republicans are set to strengthen their grip on the Senate.
Tuesday's vote was seen as a referendum on a polarising president, even though he is not up for re-election till 2020.
The election confirms a historical trend for the party that is not in the White House to make gains in the mid-terms.
House Democratic leader Nancy Pelosi - who is set to become speaker, a position she held from 2007 to 2011 - told cheering supporters in Washington: "Thanks to you, tomorrow will be a new day in America."
President Trump focused on the Senate, and praised himself by quoting a commentator.
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What's happening in House races?
The Democrats took control of the House, having gained more than the 23 seats they need to take over the lower chamber of Congress. Americans voted for all 435 seats in the House.
The Democrats could now launch investigations into Mr Trump's administration and business affairs, from tax returns to potential conflicts of interest.
They could also more effectively block his legislative plans, notably his signature promise to build a wall along the border with Mexico.
What's happening in Senate races?
Republicans are on course to expand their slim 51-49 majority in the upper chamber. This ensures Mr Trump will have a majority to confirm his executive and judicial appointments.
Democrats were always facing an uphill battle in the Senate this year because they were defending 26 races, while just nine Republican seats were up for grabs.
Key gains for the Republicans came in Indiana, Missouri and North Dakota, where they unseated Democrat incumbents.
Rick Scott is likely to defeat a Democratic incumbent in Florida, giving Republicans control of both the state's seats for the first time in more than a century.
Republican Texas Senator Ted Cruz fended off a strong challenge by Democratic rising star Beto O'Rourke.
America's partisan trenches deepen
Analysis by Anthony Zurcher, BBC News
It's a tale of two chambers.
The door to a Democratic-controlled Senate slammed shut. Donald Trump will continue to have a Republican majority ready and willing to confirm his executive and judicial appointments. The only question now is the size of his party's advantage.
In the House of Representatives, however, the story is different. The path of least resistance for Democrats to a majority in that chamber led through educated suburban districts that had long voted for Republicans, but contained voters that may have been uneasy with Donald Trump's policies and rhetoric.
One by one, those districts were carried by the Democrats. In Virginia, Illinois and Florida, moderate Republicans lost. In places like Colorado, New Jersey, Kansas, Pennsylvania, Texas and New York, Democrats are poised for victory.
It won't feel like the tsunami many on the left were hoping for, but a steadily rising tide is still lifting Democrats to enough victories to give them control of the House for the first time in eight years. With that comes the ability to stop the Trump legislative agenda in its tracks and puts some teeth in congressional oversight of his administration.
The partisan trenches in America are getting deeper. And after two years in the darkness, Democrats have a means to fight back.
What's happening in governors' races?
Governors have been chosen in 36 out of 50 states.
In Florida, left-wing progressive Andrew Gillum has conceded after an ugly battle against a Trumpist conservative, Ron DeSantis.
But Democrat Stacey Abrams - who ran to become the first black female governor in the US - refused to concede as her Republican opponent Brian Kemp took a commanding lead after a bitter campaign in Georgia.
Democrat Jared Polis is projected to win the Colorado gubernatorial race, becoming the first openly gay man to be a US governor.
Democrats also captured governorships in Michigan, Illinois and Kansas. In Kansas, Republican Trump ally Kris Kobach was defeated by a Democratic state senator Laura Kelly.
New York Democratic Governor Andrew Cuomo - sometimes spoken of as a 2020 presidential contender - cruised to a third term.
Credit: The BBC