Four midterms takeaways for 2028 White House race

Exit polls suggest the swing against Republicans was partly due to anger felt by voters at the actions of the Trump administration.

That could present a challenge to his potential successors who come from the ranks of the current leadership, including Vice-President JD Vance and Secretary of State Marco Rubio.

"The one person who has been hurt badly by this election campaign is Vance," said Karen Beckwith, a professor of political science at Case Western Reserve University in Ohio.

Vance has already sought to distance himself from defeat - and from a foreign policy adventure in Iran that was politically disastrous for his party.