WASHINGTON — Gov. Tim Walz and Sen. JD Vance met Tuesday for their first and possibly only vice presidential debate, in what could be the last debate for both campaigns to argue their case before the election.

The debate in New York hosted by CBS News gave Vance, a Republican freshman senator from Ohio, and Walz, a two-term Democratic governor of Minnesota, the chance to introduce themselves, make the case for their running mates and go on the attack against the opposing ticket.

Tuesday’s matchup could have an outsized impact. Polls have shown Vice President Kamala Harris and former President Donald Trump locked in a close contest, giving added weight to anything that can sway voters on the margins, including the impression left by the vice presidential candidates. It also might be the last debate of the campaign, with the Harris and Trump teams failing to agree on another meeting.

The role of a presidential running mate is typically to serve as an attack dog for the person at the top of the ticket, arguing against the opposing presidential candidate and their proxy on stage. Vance and Walz have each embraced that role.

Vance’s occasionally confrontational news interviews and appearances on the campaign trail have underscored why Trump picked him despite his past biting criticisms of the former president, including once suggesting that Trump would be “America’s Hitler.”

Walz, meanwhile, catapulted onto Harris’ campaign by branding Trump and Republicans as “just weird,” creating an attack line for Democrats seeking to argue that Republicans are disconnected from the American people.

A new AP-NORC poll found that Walz is better liked than Vance, potentially giving the Republican an added challenge.

After a Harris-Trump debate in which Republicans complained about the ABC News moderators fact-checking Trump, Tuesday’s debate will not feature corrections from the hosts. CBS News said the onus for pointing out misstatements will be on the candidates, with moderators “facilitating those opportunities.”

Ahead of the debate, allies of both men were lowering expectations that their candidate would deliver a decisive performance.

Sen. Amy Klobuchar, D-Minn., called Vance “an accomplished debater” and contrasted that with Walz, saying he was “not a lawyer- debater type.”

Jason Miller, a senior adviser to Trump, portrayed Walz much differently than Klobuchar. “Tim Walz is very good in debates, really good. He’s been a politician for nearly 20 years. He’ll be very well prepared for tomorrow night,” Miller told reporters Monday.

He predicted that Walz would be much more “buttoned up” than he is on the campaign trail and ready to defend his record, but “that’s not to say that JD Vance won’t be prepared tomorrow or that somehow he isn’t up to the challenge.”

Vance, speaking to reporters last week, said he didn’t “have to prepare that much” for the debate because he had “well-developed views on public policy.”

But Vance has been doing debate prep sessions where he has been joined by his wife, Usha Vance; his senior aides; Miller; and Rep. Tom Emmer, R-Minn., who has played Walz, according to a person familiar with his preparations who requested anonymity to discuss strategy. Moderating their mock debates was Monica Crowley, who served in the Trump administration, hosts a podcast and contributed to Project 2025, a conservative blueprint for remaking government that Trump claims he knows “nothing about.”

Walz’s debate prep has included sessions hunkered down in a Minneapolis hotel, with Transportation Secretary Pete Buttigieg standing in for Vance, according to a person familiar with the process who requested anonymity to discuss the campaign’s internal dynamics. Others helping in the preparations include Rob Friedlander and Zayn Siddique, who helped Harris prepare for her debate with Trump, along with other aides to Walz and the campaign. “Just because he’s an optimistic, positive person doesn’t mean he’s a pushover,” Klobuchar said.

Also Tuesday, multiple news reports indicate that Walz misleadingly claimed he was in Hong Kong during the turbulence surrounding the 1989 Tiananmen Square massacre. The Associated Press contacted the Harris-Walz presidential campaign and did not receive a response.

Earlier Tuesday, Trump campaigned in Wisconsin, stopping in a critical Democratic county that is crucial to Harris’ hopes for winning the key battleground state.

Trump is scheduled to appear at a manufacturing facility in Waunakee, a suburb of Wisconsin’s capital, Madison, in Dane County. Trump has never campaigned there and didn’t visit as president.

Trump also held an event at a museum in Milwaukee, site of the GOP convention, Wisconsin’s largest city, and home to the largest number of Democratic voters and second-largest number of Republicans. His support has softened in Milwaukee’s conservative suburbs.

Harris was scheduled to tour damage caused by Hurricane Helene in Georgia and North Carolina. She plans to visit Georgia on Wednesday and survey the devastation in North Carolina in the coming days, according to aides who spoke on the condition of anonymity to discuss the travel plans. Harris’ team has been working to coordinate her plans to avoid affecting local disaster response efforts.