DALLAS: US Republicans return to the stage Thursday to close their midterm convention, still betting that Donald Trump’s political magnetism can overcome grim election forecasts – while giving vice-president JD Vance a prime-time showcase as a potential heir.

Trump will dominate the finale of the two-day gathering, delivering closing remarks after Vance’s keynote address at the American Airlines Center in downtown Dallas.

The unusual convention has been built around a simple message: Trump may not literally be on November’s ballot, but Republicans want the president’s supporters to behave as though he is.

That strategy comes with the party under heavy pressure.

US election tracking site Decision Desk HQ projects Democrats will win the House 230-205 and take the Senate 51-49. Trump’s approval rating has languished in the low-to-mid 30s amid stubborn inflation and an unpopular war with Iran.

Trump dramatically raised the stakes in his opening night keynote Wednesday, promising a US$5,000 “Trump dividend” to every American adult if Republicans retain both chambers of Congress in November.

He also made explicit the convention’s central electoral pitch.

“I’m asking you to pretend that I’m on the ballot – I’m on the ballot, I’m on the ballot – just one more time,” he said.

He strongly defended the Iran war, predicting victory would bring down oil prices, and warned that the United States would become a “communist country” if Democrats prevail in the election.

Heir apparent?

Vance’s appearance adds intrigue to the closing night.

The 42-year-old vice-president is widely regarded as an early front-runner for the 2028 Republican presidential nomination, although he has said he will not make a decision until after the midterms.

His place immediately before Trump’s closing remarks gives him one of the most prominent speaking slots of the convention and an opportunity to address a party already beginning to consider its post-Trump future.

But in the more immediate contest, Republicans need Vance and other party figures to help deliver Trump’s voters in an election in which the president himself is absent from the ballot.

Republicans also hope to use the closing night to promote tax cuts, immigration enforcement and other administration policies while depicting Democrats as increasingly extreme.

The convention has resembled an extended Trump rally more than a traditional party meeting, with no nominations or formal business and more than 50 speakers or presentations each night.

The atmosphere inside the arena on Wednesday was festive despite the political headwinds. Yet not all Republicans have embraced the experiment.

Numerous lawmakers in competitive races chose to remain in their districts rather than spend valuable campaign time in Dallas, while both convention nights were facing competition from the opening games of the NFL season.

Those who have shown up will be looking for evidence that Vance can emulate Trump in energising the voters who powered the flamboyant billionaire’s return to the White House.

And Vance, whether he acknowledges it or not, will be speaking to a party already asking who might inherit those voters when Trump is no longer the headline act.

“If the American people give Republicans another chance to govern, we’re going to create more prosperity,” Vance told Fox News after Trump’s speech.

“And we want the American people to share in that prosperity.”