President Donald Trump on Wednesday promised $5,000 to every adult American if Republicans retain control of Congress in November, coupling the extraordinary claim with a plea for his supporters to "pretend" he was on the ballot.

"If the Republicans win, you win with us and you get $5,000. It will be called the Trump dividend," he told the Republican midterm convention in Dallas, as the party struggles in polls against the Democrats.

The president did not say where the money would come from -- with the theoretical bill likely topping $1 trillion -- citing only that "our country is making so much money."

Doubling down on his bet that he can help Republicans to defy opinion polls and retain both houses of Congress on November 3, Trump said "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 told the crowd.

Opinion polls overwhelmingly show that Trump's approval ratings are in the low 30s, as voters become increasingly angry about high prices and the war he launched against Iran.

Decision Desk HQ projects Democrats to win the House 230-205 and the Senate to finish 51-49 in their favor in November.

Trump defends Iran war
Trump strongly defended the unpopular Iran war, predicting victory and linking it directly to lower oil prices -- before suggesting the strategically vital Strait of Hormuz should be renamed after him.

"Food prices and almost every other item are rapidly going down. And by the way oil will be going down as soon as we win the war with Iran, which is taking place right now," Trump said.

Trump also echoed other Republicans at the convention stirring up what he said was a wave of communism threatening the United States.

"It's going to be a communist country if they win," he said.

"Your vote will decide whether our country stumbles at the starting gate of the next 250 years or surges forward and never ever looks back," he said.

Trump is due to return for the convention finale Thursday, after a keynote address from Vice President JD Vance.

Cabinet members, congressional leaders and candidates in closely watched House and Senate races are also on the program.

The central Republican gamble is whether Trump can mobilize voters personally loyal to him even when he is not actually running, without further alienating independents who have soured on his presidency.

Political headwinds
Inside the American Airlines Center, there was little sign of Republican anxiety about November.

The convention even featured a video address from Democratic Senator John Fetterman, who has become increasingly at odds with his party's left wing over issues including Israel.

Republicans highlighted tax cuts and immigration enforcement, touting boosted manufacturing and lower prescription drug prices.

The cavernous arena was festooned with Trump posters as supporters milled around in sequined jackets patterned with his name, image and the American flag, some topped with ten-gallon hats.

Food stalls hawked overpriced snacks while merchandise stands did brisk business in T-shirts, mugs, posters and copies of the latest literary offering from the Trump clan, "Under Siege" by the president's second son, Eric.

Despite the political headwinds facing Republicans, the mood was festive. Chants of "USA! USA!" -- familiar from Trump's campaign rallies -- echoed around the hall as the national anthem opened the program.

Large gaps remained in the stands, although the arena filled steadily as afternoon turned into evening.

Susan Kokinda, 77, a conservative podcaster who traveled to the gathering from Michigan, told AFP she expected Republicans to "do just fine" in November.

"The conventional wisdom is the party in power loses. But I always say Donald Trump is not a conventional president, and he's reshaping the Republican Party," she said.

The gathering is the first Republican national convention held specifically for a midterm election, although no candidates are being nominated and no formal party business is planned.

Instead, organizers have constructed what amounts to a two-night television rally touting Trump's record and Republican candidates.

More than 100 House members and candidates were expected, with over 50 speakers or presentations scheduled each night.