Tens of millions of voters delivered a scathing rebuke to President Donald Trump, who lashed out on social media after beginning his lame-duck era.
"I wasn't on the Ballot and if I was, we would have won IN A LANDSLIDE! Thank you for your attention to this matter", he wrote on social media as it grew clear Republicans were in danger of losing their congressional majorities.
Trump then said he would accept the election results.
In the House, Democrats flipped Republican seats in states including Kentucky, New Jersey and North Carolina, showing strength even in solidly conservative districts.
In the Senate, Democratic state representative James Talarico withstood a barrage of outside spending to defeat scandal-plagued Republican Attorney-General Ken Paxton in Texas, a state that voted for Trump by 14 percentage points two years ago.
In South Carolina, pediatrician Annie Andrews became the first Democrat to win a Senate seat since 1998, a stunning victory over Trump's hand-picked candidate Darline Graham in a state that he carried by nearly 18 percentage points in 2024.
The Democrats also flipped the Senate seat in North Carolina from Republicans when governor Roy Cooper defeated Michael Whatley, a former chairman of the Republican National Committee, who was backed by Trump.
Democrat Josh Turek turned Iowa blue, defeating Republican Ashley Hinson, while Democrat Sherrod Brown flipped Ohio, beating incumbent Jon Husted.
In Kansas, Democrat Adam Hamilton triumphed over Republican incumbent Roger Marshall - who was backed by Trump - the first time the party won a US Senate seat in the state for 94 years.
"In sweeping and decisive victories, the American people have rebuked the depravity, corruption and incompetence of the man named President Donald J Trump," incumbent Democratic senator Jon Ossoff, the projected winner in Georgia, told supporters at a victory party.
Ossoff is being touted as a potential 2028 presidential candidate.
Democrats held on to three House districts in Florida that Republican lawmakers had redrawn earlier in 2026, all of which backed Trump by at least nine percentage points.
Midterm elections are typically viewed as a referendum on the president, and that is especially true for Trump, who dominates attention like no other politician.
Trump himself told his supporters to "pretend I'm on the ballot" and held dozens of rallies in the closing weeks.
According to exit polls half of voters nationwide said they saw the 2026 midterm elections as an opportunity to rebuke the president, and three-quarters said they are "angry" or "dissatisfied" with the way the country is headed.
In addition, 70 per cent of voters surveyed said they wanted Congress to provide more checks and balances on the president.
History is against Republicans: the sitting president's party has lost ground in Congress in all but two midterms since World War Two.
Trump's approval rating is hovering near his career lows, with voters frustrated by war with Iran, higher fuel prices and wider affordability concerns.
Opinion polls show voters are most concerned about affordability and disapprove of Trump's handling of the issue.
His tariffs on imports and his decision to attack Iran in February raised prices for consumers.
There are 47 US House races widely seen as competitive, according to a Reuters analysis of the leading election forecasters.
If the other contests all proceed as predicted, Democrats would need to win only 13 of those races to secure a majority.
