It's still too early to determine whether Democrats will be able to net the four Senate seats and three House seats they need to win a majority in both chambers, with millions of votes still to be counted across the country.
In North Carolina, Democratic former Governor Roy Cooper easily defeated Trump-backed Republican Michael Whatley to win a Republican-held seat, media outlets projected on Tuesday.
Senator Jon Ossoff, a Georgia Democrat widely seen as a potential 2028 presidential candidate, defeated US Representative Mike Collins in a contest that was once considered competitive but moved out of reach for Republicans amid US President's Trump's declining approval ratings.
In New Hampshire, Democrat Chris Pappas kept the state's open Senate seat in Democratic hands, defeating Republican John Sununu.
In Florida, Republican Senator Ashley Moody fended off Democrat Angie Nixon but was ahead by only about three percentage points in a state Trump carried by 13 points in 2024, according to a vote count compiled by Reuters and USA Today, which are partnering this year to collect live election results.
Democrats held onto three House districts in Florida that Republican lawmakers had redrawn earlier this year, all of which backed Trump by at least nine percentage points.
Democrats were favoured to win the House, while the Senate battle was unfolding across several closely contested states, as millions of Americans cast ballots in an election that served as a referendum on the first two years of Trump's second term. Trump himself told his supporters to "pretend I'm on the ballot."
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 want 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.
Led by Trump, Republicans have portrayed Democratic candidates as radical, un-American and even communist, labels Democrats flatly reject.
The president has sought to energise his base with more than two dozen campaign rallies since the start of October, most in states he easily won in 2024, underscoring Republicans' defensive posture.
Opinion polls show voters are most concerned about affordability and disapprove of Trump's handling of the issue. His tariffs on imports, many of which the courts threw out, 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.
But Democrats have little margin for error in the Senate. The party must defend all of its current seats while winning at least two states that voted for Trump by a double-digit margin two years ago, such as Alaska, Iowa, Kansas, Nebraska, Ohio, South Carolina and Texas.
Legal observers and Democrats have warned that Trump, who has long falsely claimed that US elections are rigged, may attempt to challenge Tuesday's results if Republicans lose.
The US Justice Department said it had deployed 1,000 election monitors and observers to all 50 states in what it called the largest Election Day monitoring effort in history.
Democrats criticised the plan as potential voter intimidation.
