Democrats look set to take the majority in the House of Representatives but fail to win back the Senate after the “blue wave” of historic support they hoped for failed to materialise.
Multiple US broadcasters projected that the Democrats would take the House. It will allow them to block Donald Trump’s laws and launch a string of investigations into his administration.
However the Republicans looked on course to hold – or possibly even increase – their majority in the Senate, a result which Mr Trump is likely to use as proof that the night was not as bad as feared.
In the most closely watched race of election night, Ted Cruz was projected to see off Beto O’Rourke, the Democrat who became a nationwide pinup for liberals, and win re-election as Texas senator.
Pundits credited Republican turnout from a support base fired up by Mr Trump with robbing the Democrats of the landslide election they were hoping to secure.
There were also a string of historic milestones, with the first Muslim congresswoman, first openly gay male governor and the youngest ever congresswoman (aged 29) all being elected.
Losing the House will be a major political headache for Mr Trump. His political opponents will now have veto over any legislation he proposes, ending the Republican’s control over both wings of Congress. That could jeopardise the president’s hopes of securing funding for his US-Mexico border wall, further unpicking Barack Obama’s healthcare legislation and implementing a new tax cut for the middle classes.
Holding the majority also means Democrats take control of the House’s committees, meaning they can launch a string of damaging investigations into the Trump administration and call witness to testify.
However the White House will be buoyed by projections that the Republicans will retain their majority in the Senate, and possibly even increase it.
The Senate electoral map had always looked difficult for the Democrats, with 10 of their incumbent senators fighting to win re-election in states which Mr Trump won in 2016.
On the night the Republicans flipped Indiana, were hopeful of repeating the feat in a handful of other Democrat seats and managed to hold Tennessee, which looked at risk.
Lindsey Graham, the Republican senator for South Carolina, credited Mr Trump with “creating enthusiasm” among his supporters, adding: “President Trump is well on his way to getting re-elected.”