Control of Congress still hangs in the balance a day after the US midterms, dampening Republican hopes of a “wave” of victories.
As vote counts continue, Democrats were projected to win a crucial Senate seat in Pennsylvania with other key battlegrounds too close to call.
Republicans need to gain just one Senate seat to take control.
Republicans are still favoured to win the House, although Democrats are putting up resistance in some races.
All 435 seats in the House of Representatives and a third of the Senate were up for grabs.
Though President Joe Biden, a Democrat, is not on the ballot, the midterms will shape the fate of his agenda.
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Republicans can still pick up the five seats they need to win the House, but the party has so far failed to land a knockout blow as Democrats notch victories in highly competitive districts.
In the battle for the Senate, left-wing Democrat John Fetterman – who has been recovering from a stroke – is projected by CBS to have beaten Trump-backed celebrity doctor Mehmet Oz in potentially pivotal Pennsylvania.
Another critical Senate race, between Democrat Raphael Warnock and Republican challenger Herschel Walker in Georgia, is on a knife-edge, and could even end up in a run-off if neither candidate gets more than 50% of the vote.
The results of other key Senate races in Wisconsin, Arizona and Nevada were also still in play.
Which party holds sway in the upper chamber of Congress may not be known for days, or even weeks.
Elections for state governors also took place in several states.
Republicans were expected to hold on to governors’ mansions in the key states of Texas, Florida and Georgia.
Florida’s Ron DeSantis and Texas’s Greg Abbott are future possible Republican presidential contenders.
Mr Abbott has consigned Democratic challenger Beto O’Rourke to his third campaign defeat in the past four years.
The Democratic candidate in Georgia, Stacey Abrams, conceded the race to the Republican Governor Brian Kemp.
But in New York and Michigan, Democrats were projected to see off unexpectedly stiff Republican challenges in governors’ races.
And the bitterly fought race for the governor’s mansion in Arizona – in which Republican Kari Lake had appeared to have the edge over Democrat Katie Hobbs – has been rated as leaning Democrat by CBS, based on incomplete results.
A handful of trailblazers emerged in other projections:
In Maryland, Democrat Wes Moore is set to become the third African American ever elected as governor
In Florida, 25-year-old Democrat Maxwell Frost is on course to become the first Gen Z member of Congress
Markwayne Mullin, an Oklahoma Republican and member of the Cherokee nation, is poised to become the fourth Native American ever elected to the US Senate
The US is set for its first openly lesbian woman elected as governor, with Democrat Maura Healey to become the top official in Massachusetts
Maryland became the 20th state to legalise recreational marijuana, with similar ballot measures put to the vote on Tuesday in Arkansas, Missouri, North Dakota and South Dakota
Exit polls have suggested the main issues for voters were inflation and abortion.
Despite leveraging wafer-thin congressional majorities to lower prescription drug prices, expand clean energy and revamp US infrastructure, Mr Biden’s popularity has taken a pummelling amid the worst inflation in four decades.
But Republicans had their own political vulnerability on the issue of abortion following the conservative-dominated Supreme Court’s decision this year to roll back a US constitutional right to the procedure.
The ruling energised liberal voters around the country, raising Democratic hopes they might defy the historical political gravity that typically weighs on a governing party in the midterms.
On Tuesday, voters in Vermont, California and Michigan decided to enshrine abortion rights in their state constitutions, preventing any future bid by the legislature to introduce restrictions.
Kentucky was deciding in a ballot measure whether to rule out protections for abortion.
According to exit polls by the BBC’s US partner CBS News, abortion was the top issue for Democratic voters, while Republicans and independents rated inflation as their top issue