President Donald Trump capped the first day of his Republican Party's first-ever midterm convention by proposing to pay every US adult a 5,000 dollar "Trump dividend" if his party wins November's congressional elections.

Trump delivered the extraordinary overture during a primetime speech that lasted nearly two hours and firmly placed him at the ‌center of the midterm campaign at a time when his sagging approval ratings could weigh on Republicans' chances.

Vice President JD Vance will give the keynote address on Thursday night, though Trump is scheduled to make closing remarks to bring the made-for-television two-day event in Dallas to an end.

With Trump constitutionally barred from seeking a third term, Vance's speech could serve as an early audition for the 2028 presidential election and offer clues about how he would lead a party reshaped by Trump.

It was not immediately clear how the 5,000 dollar payments would work or whether they would be legal. The proposal would likely cost more than 1 trillion dollars, with approximately 270 million ⁠US adults, and could require the approval of Congress.

The convention's focus on Trump – some Republicans have dubbed it "Trumpapalooza" – amounts to a risky bet that he can mobilize the voters who carried him to the presidency two years ago, despite opinion polls showing his popularity is at an all-time low.

But it remains to be seen whether his campaign-style speech will appeal to the critical swing voters who have drifted away from Trump's party amid growing dissatisfaction with the cost of living and the war on Iran.