New York (AFP) - US vice presidential contenders J.D. Vance and Tim Walz took on the crisis in the Middle East as they met Tuesday for what could be an unusually important undercard debate, competing for decisive votes weeks before the election.

The showdown between Walz, the Democratic Minnesota governor chosen by Kamala Harris, and Vance, the Republican senator from Ohio who is Donald Trump’s running mate, is likely to be the last of the 2024 campaign.

Trump has refused a second debate with Vice President Harris, meaning this could be the final chance to see the two tickets go head to head.

The first question of the night was on Iran’s missile attack on Israel and Walz immediately turned his fire on Trump’s foreign policy record, slamming the ex-president for his “turn towards” Russia’s Vladimir Putin” and his withdrawal of the United States from the 2015 Iran nuclear disarmament deal, known as the JCPOA.

“As much as Governor Walz just accused Donald Trump of being an agent of chaos, Donald Trump actually delivered stability in the world,” Vance countered.

“And he did it by establishing effective deterrence. People were afraid of stepping out of line.”

Vance, 40, and Walz, 60, each claim to be the true voice of the crucial swing states – including Michigan and Wisconsin – that could decide an election that remains on a knife-edge with five weeks to go.

History suggests vice-presidential debates rarely move the dial much. But in an election campaign that has seen Harris step in for President Joe Biden unprecedentedly late in the game, Tuesday’s contest may have added significance.

Biden offered words of encouragement for Walz, telling him in a post on X ahead of his big night: “Coach, I got your back tonight!”

The race has seen Vance and Trump use increasingly divisive rhetoric and even falsely accuse immigrants of eating people’s pets – meaning the debate could make for fiery television.

“It will whet a lot of people’s appetites for November 5,” Thomas Whalen, an associate professor of social sciences at Boston University, told AFP.

But the debate itself risked being overshadowed by Mideast tensions, after Iran launched ballistic missiles against Israel, which said it largely repelled the attack.

Trump, visiting swing state Wisconsin on Tuesday, focused on the crisis, insisting that “if I were in charge, today’s attack on Israel never would have happened.”

Should Harris and Walz win, he warned, “the world goes up in smoke.”

Trump told Vance to “have fun” when he was asked what advice he would give, praising his running mate as a “warrior.”

Harris for her part pledged her “unwavering” commitment to the security of Israel after Iran launched what she called “a reckless and brazen attack” on America’s ally.

The CBS clash comes as several states dig out from enormous storm Helene, which has left at least 150 people dead and brought misery to many thousands more.

- ‘High drama’ -

Walz and Vance were each picked by their bosses to reach out to voters in the Midwestern battlegrounds where, thanks to the country’s idiosyncratic electoral college system, a few thousand votes could determine who wins the White House race.

Both are military veterans with strong blue-collar credentials. Vance authored the Rust Belt memoir “Hillbilly Elegy” while Walz boasts a folksy persona as a former teacher and football coach.

The similarities end there.

The combative Vance shares Trump’s penchant for courting controversy, whether by smearing Democrats as “childless cat ladies” or by boosting false claims that Haitians living in an Ohio town ate residents’ pets.

His goal will be to overcome polls that initially had him as one of the least popular VP nominees in history, after a series of previous comments on women and abortion were unearthed.

“Vance has to be careful, because I think a trap has been laid for him,” said Whalen.

The cheery Walz will be seeking to introduce himself to a public that barely knows him, after Harris’s swift rise to replace Biden as the Democratic nominee.

He became a hit with Democrats for branding Vance and Trump “weird” and for his progressive politics – but that will be a target for Vance as he and Trump seek to paint Walz and Harris as “Marxists.”

Vance “is going up against a moron, a total moron,” Trump said in an interview Monday on Fox Nation.