As Pete Buttigieg takes the stage Wednesday night for the Democratic debate in Atlanta, he is likely to be a new focus of criticism as an emerging leader in the presidential polls. How he reacts to the expected zingers from his rivals could be an important test of his candidacy.

Former Iowa governor Tom Vilsack, a close friend of former vice president Joe Biden who has yet to endorse a candidate in the presidential race, compared Buttigieg to “the newest gadget or gimmick” that fascinates people as they flip through a holiday catalogue. In an interview, he suggested that the South Bend, Ind., mayor needs to prove he can withstand the heightened scrutiny of being a top-tier candidate.

“We’ll see about Mayor Pete,” Vilsack said. “He may be able to take a punch. He may not. We just don’t know.” He added, “The vice president has shown he can take a punch, and I don’t know that the rest of these folks have actually had to take a punch yet, much less show they can take one now.”

Other candidates have shown frustration in recent weeks at the rise of the 37-year-old mayor of Indiana’s fourth-largest city, taking aim at his relative inexperience and his struggle to attract black voters. The crowded debate stage Wednesday, featuring 10 Democratic contenders, could provide ample opportunity for that rancor to boil over.

Sen. Amy Klobuchar (D-Minn.), who like Buttigieg is pitching herself as a Midwestern pragmatist, has tried to differentiate herself from him by emphasizing she is “the one from the Midwest that’s actually won in a statewide race over and over again.”

Klobuchar has also questioned whether a woman with Buttigieg’s level of experience would be enjoying the same success or attention. “Of the women on the stage . . . do I think we would be standing on that stage if we had the experience that he had? No, I don’t,” Klobuchar told CNN earlier this month. “Maybe we’re held to a different standard.”

Sen. Kamala D. Harris (D-Calif.), meanwhile, seemed taken aback this week to learn Buttigieg had used a stock photo of a mother and child in Kenya to promote his proposal for black Americans and suggested it showed he was ill equipped to lead a diverse country.

“He’s going to have to answer for that,” Harris said after laughing. “The Democratic nominee has got to be someone who has the experience of connecting with all of who we are as the diversity of the American people.”

The Buttigieg campaign declined to comment for this article, though his senior communications adviser hinted that his advisers were expecting Buttigieg to be a debate target. She tweeted a “Game of Thrones” image of Jon Snow, one of the saga’s heroes, fending off an onslaught of attackers.

The South Bend mayor entered the race as a little-known figure, but he recently surged to first place in a poll of Iowa voters and has been rising in New Hampshire. At the same time, Quinnipiac University’s newest South Carolina poll showed Buttigieg with less than one percent support among black voters, prompting questions about whether he can galvanize the Democratic Party’s diverse base.

Wednesday’s debate, sponsored by The Washington Post and MSNBC, comes at a turbulent political moment as the capital is consumed with impeachment proceedings against President Trump. The Democratic race itself remains fluid, with several candidates dropping out in recent months and others making last-minute entries, including former Massachusetts governor Deval Patrick and potentially former New York mayor Mike Bloomberg.

That murkiness has some Democratic donors and strategists fretting that the primary could languish for months with no clear winner. So far, Democrats have engaged in a game of shoot the leader: First Biden, then Harris, then Sen. Elizabeth Warren (D-Mass.) have seen surges of momentum, only to attract sharp attacks from their rivals on the debate stage.

It is unclear whether Warren will join any such verbal assaults on Buttigieg on Wednesday. For weeks, the mayor has been running ads that criticize Warren and Sen. Bernie Sanders (I-Vt.) for their embrace of a Medicare-for-all health plan, and he has denigrated Warren’s position as “my way or the highway.”

Buttigieg leveled some of the sharpest attacks on Warren in the last debate. Warren’s style has been to avoid directly criticizing Buttigieg — or the other Democrats — but she recently sharpened her stump speech to criticize candidates who take corporate donations and offer proposals that “nibble around the edges.”

“I’m not running some consultant-driven campaign with proposals that have been carefully crafted not to offend big donors,” Warren said at a town hall in North Las Vegas on Sunday, in a comment seen by many as a shot at Buttigieg. “I passed that point a long time ago.”

She added that the Democratic nominee needed “big ideas” to inspire voters and to help those who need it most. Buttigieg, like Biden, has proposed a government-run health plan as an option, rather than making it universal and mandatory, as under Medicare-for-all.

“I get it. It’s easy to give up on big ideas. You can make yourself so smart and so sophisticated,” Warren said. “But here’s the thing: When we give up on those big ideas, we give up on the people who would be touched by those ideas.”

Biden, who has been slipping in the Iowa polls, has mostly used a light touch in dealing with Buttigieg, though he has tried to take back the phrase “Medicare for all who want it” — first used by Buttigieg’s campaign — as an approach he came up with first.

Biden will have to decide whether to go further than that Wednesday. A Biden supporter this week circulated video of Buttigieg speaking at a tea party event in 2010, expressing the possibility of finding common ground with the deeply conservative group as he campaigned for Indiana state treasurer. The tea party is anathema to many Democratic voters.

Though Buttigieg has not directly attacked Biden, he has unmistakably presented himself as an alternative to the former vice president in courting the Democratic Party’s centrist wing, and at times he has referred to “the failures of the old normal.”

Buttigieg may be most vulnerable Wednesday on issues of race. He comes into the debate fresh from a controversy in which his campaign touted the backing of more than 400 South Carolinians for his “Douglass Plan for Black Americans,” even if they did not endorse Buttigieg himself. That led some signatories to feel their positions had been misrepresented.

Last week, Johnnie Cordero, chairman of the Democratic Black Caucus of South Carolina, told the Intercept that the Buttigieg campaign had used his name prominently even though he had not endorsed the plan. Two other black leaders also expressed reservations about how the campaign had characterized their support.

For days, the campaign insisted it had done nothing wrong, but on Monday, Buttigieg called the incident a “miscommunication” and a “learning experience,” according to NBC News.

“We have a lot of people who are supporting [the Douglass Plan] but a few people who didn’t believe the message reflected their support,” Buttigieg said. “So we are clearing that up.”

Meanwhile, it also emerged that Buttigieg’s campaign had used a stock photo of a woman and child in Kenya to promote the Douglass Plan; the campaign said the images have since been removed from its website and apologized for their inclusion.

On Monday, Harris responded forcefully when reporters asked her to weigh in on the controversy, after initially seeming surprised. “I’m sure someone agrees that was a big mistake,” Harris said. “He’s going to have to answer for that. It’s — I don’t have words to describe that.”

In his continued efforts to court black voters, Buttigieg on Monday addressed an audience made up largely of students from historically black Morehouse and Spelman colleges in Atlanta. He cited former Georgia gubernatorial nominee Stacey Abrams and her work on voting rights, while facing questions about the fallout in South Bend when a white police officer shot a black resident earlier this year.

Buttigieg was light on details, often answering with phrases like “There’s no easy fix for that” or “We’re not going to solve it all today.”

That left Spelman freshman Kyra Gines wanting more, especially when it comes to details of the Douglass Plan.

“I think he’s good at being a politician,” Gines said. “He knew his audience well, and he knew the buzz lines that would do well . . . . In terms of actual content, I think there were some things to be desired in how he stepped around questions. But again, that’s politicians.”

Even candidates who failed to qualify for the debate stage have joined in the criticism of Buttigieg, sometimes expressing disbelief that a candidate with such a short resume has pushed them out of the spotlight.

At a Friday house party in Nashua, N.H., Colorado Sen. Michael F. Bennet joked about South Bend’s small size.

“The school district that I ran had a budget three times the size of South Bend, which is substantial,” said Bennet, who once headed Denver’s school district. “I’ve won two national elections in a swing state. I won more votes than any politician has ever won in the state of Colorado, the last time I ran.”

He added, “Mayor Pete won eight thousand votes the last time he ran for mayor. I’m not denigrating it, but it’s a very different set of experiences.”

Maggie Penman, Holly Bailey and David Weigel contributed to this report.