US vice presidential contenders J.D. Vance and Tim Walz clashed on abortion and migration in their televised debate Tuesday, but ended up repeatedly circling back to one subject — Donald Trump.

In a largely polite encounter, Republican Vance and Democrat Vance dug deeper into the details of policy than presidential candidates Trump and Kamala Harris did during their clash in September.

But with Minnesota governor Walz attacking Republican former president Donald Trump, and Ohio senator Vance singing his praises, the debate was often overshadowed by the billionaire, whose name came up more than 80 times — twice as many as Harris.

An initially nervy Walz lashed out early on over migration, one of the key subjects for voters in November, criticizing Vance for boosting bogus stories about Haitian migrants.

"By standing with Donald Trump and not working together to find a solution, (immigration) becomes a talking point," Walz said when the debate turned to tensions in Springfield, Ohio over migrants.

"And when it becomes a talking point like this, we dehumanize and villainize other human beings," Walz said during the CBS debate.

'Barbaric'

One of the few heated clashes came on abortion, a hot-button issue since a Supreme Court packed with judges picked by Trump overturned the national right to abortion in 2022.

Vance accused Democrats of taking a "very radical pro-abortion stance" who backed what he called "barbaric" laws. Walz hit back saying he was "pro-women."

Trump also came up as the "veep" rivals took on the crisis in the Middle East, with the first question of the night coming on Iran's missile attack on Israel.

Walz 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 deal.

"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.

Walz faced some awkward questions, particularly when he was forced to admit he "misspoke" about whether he had been in Hong Kong during the 1989 Tiananmen Square protests in China.

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.

It is likely to be the last of the 2024 campaign since Trump has refused a second debate with Harris. Polls showed Harris won that clash after she riled Trump on several topics including the sizes of crowds at his rallies.

It is also a chance for Americans to be introduced to the two men who would be a heartbeat away from the presidency -- or next in line should an aged president step aside.

'Coach' Walz

Vance, 40, and Walz, 60, both claim to be the true voice of the crucial Midwestern swing states that could decide the tight election.

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 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.

Walz became a hit with Democrats for branding Vance and Trump "weird" and for his progressive politics.

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!"

Trump, visiting swing state Wisconsin on Tuesday, had earlier focused on the Mideast 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."

The 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.