CHARLESTON, South Carolina — The Palmetto State was never going to be a strong suit for Pete Buttigieg, who has been criticized for his record on race as mayor of South Bend, Indiana, making the Democratic primary tougher in a state where the Democratic electorate is 60% African American. And appealing to union members here has its challenges, as well, since several of his competitors have long-standing relationships with unions.

Still, Buttigieg made the effort Monday at a protest by McDonald's workers demanding a pay increase to $15 an hour. It ended up being a brief visit, however, as hecklers drowned out Buttigieg's call for higher wages to slam him for his record as mayor.

"I don't care who you're supporting for president. You deserve $15 an hour. You deserve a union, and I stand with you," a shirt-sleeved Buttigieg said, after marching around a block with workers wearing red T-shirts with the slogan Unions for All. "No matter who you support, we support you, we stand together and we will not rest until one job is enough in the United states of America … we will be with you every step of the way," the former mayor said.

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As McDonald workers – many of whom get paid the federal minimum wage of $7.25 an hour – yelled, "We work! We sweat! Put 15 in our check!" another group was facing Buttigieg, taunting him. "Where was 15 in South Bend? He can't be our president!" yelled the protestors, who said they had come to support their union compatriots and did not know Buttigieg would be there.

Buttigieg hustled out, declining to take questions from reporters.

The former mayor scored a stunning, if very narrow, victory in Iowa and placed second in New Hampshire, boosting his supporters' hopes that he could be the moderate alternative to Sen. Bernie Sanders of Vermont. But Buttigieg struggles more in states with substantial minority populations. He placed third in Nevada, which has a strong Latino community, and is running fourth or fifth in polls in South Carolina, the first primary contest state with a large African American population.

"He actually co-opted this march," says Larry Dean, 27, who was at the event with a group called Black Youth Project 100. "I don't think he has the interests of young black people" at heart, adds Dean, who is considering both Sanders and Sen. Elizabeth Warren of Massachusetts in Saturday's South Carolina primary.