DALLAS โ€” President Donald Trump tried to turn one of his biggest political vulnerabilities into a strength for Republicans here Wednesday, making the war with Iran a key focus of his speech at the partyโ€™s midterm convention.

โ€œDoes anybody here think that Iran should have a nuclear weapon? Anybody?โ€ Trump asked the crowd at American Airlines Center, articulating the administrationโ€™s core argument for attacking Iran.

The audience responded loudly and decisively: โ€œNo!โ€

Trump also repeated a claim he made to reporters earlier in the day.

โ€œThe war will be over very shortly after the election,โ€ Trump said. โ€œTheyโ€™re hanging out for dear life, hoping that we lose, so they can deal with dumb, weak Democrats and they can have their nuclear bomb. But weโ€™re not going to let that happen.โ€

The war Trump once predicted would last only four or five weeks is now in its seventh month. A recent NBC News Decision Desk Poll powered by SurveyMonkey found that 69% of Americans disapprove of Trumpโ€™s handling of the war. The share of Republicans who say they strongly approve of his handling of the war has dropped 18 percentage points since the spring and now stands at 30%.

Several people at the convention who spoke to NBC News said Trump has earned their trust on the war.

U.S. President Donald Trump.
Trump spoke at the Republican National Convention in Dallas on Wednesday night. Justin Sullivan / Getty Images

โ€œAny good thing in life is worth waiting for, and so if you put the Iran war and its ultimate conclusion in that context, I think that puts a slightly different light on it,โ€ said Jack Etheridge, an alternate delegate from Ohio. โ€œI mean, letโ€™s face it: The election is part of the timeline. The Iranians are taking advantage of that, I think, for their own purposes, but I think the reality is no one believes that Iran is going to defeat the United States.โ€

Others echoed Trumpโ€™s demand that Iran not develop or possess a nuclear weapon.

โ€œThey are not just a bad dictatorship like China or Russia. They are an extremist theocratic dictatorship, and they would drop a nuclear bomb on Europe,โ€ said David Lovlien, a county commissioner in Merrimack County, New Hampshire. โ€œWe are going to save so many lives doing what we are doing over there versus doing nothing.โ€

Vince Galko, a former top Pennsylvania GOP official, conceded that higher gas prices brought on by the war have stung.

โ€œBut,โ€ Galko added, โ€œI also think consumers can afford to look at $4 gas for a few weeks rather than looking at a mushroom cloud over their kidsโ€™ school.โ€

Sen. Rick Scott, R-Fla., said itโ€™s on Trump to explain and sell the war to Americans.

โ€œIf you explain to people, โ€˜OK, hereโ€™s your choice, would you like us to stop Iran from trying to kill or allow them to kill us?โ€™ I think itโ€™s a good choice. I can defend it,โ€ Scott said. โ€œI think heโ€™s done the right thing.โ€

In his speech Wednesday, Trump predicted that oil and gas prices would come down once the war ends.

โ€œYou know, it happens to me all the time. Guys come up, you know, โ€˜I wish you didnโ€™t do the war in Iran; gasolineโ€™s up,โ€™โ€ said Trump, dramatizing a conversation that he said ends with him winning the argument.

โ€œLet me ask you one question: Can Iran have a nuclear weapon? Absolutely not! Well, then Iโ€™m right โ€” then I win!โ€