President Donald Trump and former President Barack Obama campaigned in rival battleground states on Saturday, opening the final weekend before Tuesday's midterm elections that will decide control of the House and Senate. Both parties focused their resources on a narrowing list of contested seats.

Mr Trump spent the weekend courting Republican base voters, two days after a rally in Rock Hill, South Carolina, for Senator Darline Graham. Ms Graham was appointed by Governor Henry McMaster after her brother, Senator Lindsey Graham, died in July. The White House has framed the midterms as a referendum on the president's second-term agenda.

Mr Obama returned to the trail for Democratic candidates, urging supporters to turn out and arguing that a Democratic House would restore checks on the administration. Democratic Party organisers said the former president's appearances were aimed at younger and Black voters, whose turnout fell in recent cycles. Early voting continued in many states over the weekend, with tens of millions of ballots already cast according to the University of Florida Election Lab.

The South Carolina contest has become an unexpected flashpoint. A New York Times/Siena poll showed Ms Graham and her Democratic challenger, the paediatrician Annie Andrews, tied at 48 per cent each, while other surveys gave the Republican a slight lead. A Democratic win in a state Mr Trump carried comfortably would significantly complicate Republican hopes of holding the Senate.

Strategists in both parties said the final 72 hours would turn on turnout rather than persuasion. Republicans hold narrow majorities in both chambers, meaning a handful of seats could shift the balance of power for the remainder of Mr Trump's term. Polls close on Tuesday evening, with results in the tightest races potentially taking days to confirm.