Washington — Former South Bend Mayor Pete Buttigieg fired back at Senator Bernie Sanders over attacks on the big-money donors to his presidential campaign, saying he is not going to turn away support from anyone who wants to help defeat President Trump in November.

Sanders, of Vermont, claimed during Friday's Democratic debate in Manchester, New Hampshire, and again Sunday in an interview with "Face the Nation" that Buttigieg has received donations from 40 billionaires and as a result would not aggressively go after the industries they represent.

"I've never hesitated to stand up to industry," Buttigieg said Sunday on "Face the Nation" when asked about Sanders' claims. "We sued the pharmaceutical industry when opioid makers ravaged our community, and I'm campaigning right now for higher taxes for the wealthy and for corporations to finally have to pay their fair share, and my campaign has been built from the grassroots."

Buttigieg noted that South Bend "is not an establishment powerhouse," and said his campaign has succeeded because the message and vision he is offering has resonated with voters of all stripes.

"At a time like this, if somebody is ready to help us put together the campaign that's going to defeat Donald Trump, then I welcome that support no matter how they voted in the past, no matter if they've got a lot of money or not," he said. "I want their help because let me tell you, Donald Trump and his allies right now are doing everything they can to hold on to power."

Buttigieg said that Mr. Trump's reelection effort has deep pockets, which underscores the need for Democrats to unify around a candidate in order to keep the president from winning a second term.

"We need to go into that fight with everything we've got, and I'm not going to define my campaign by whose help we reject or whose support we turn away," he said. "This is a moment to bring everybody that we can into common cause just as we have to unify the country after we do win."

Both Buttigieg and Sanders received a boost last week following the Iowa caucuses, the results of which have slowly trickled out after a delay in their reporting. Buttigieg topped the Democratic field in state delegate equivalents, while Sanders maintained the lead in the "popular vote" final choice, leading both candidates to claim victory.

The next contest comes Tuesday, when voters in New Hampshire head to the polls for the first-in-the-nation primary. The latest CBS News Battleground Tracker poll shows Buttigieg four points behind Sanders in the Granite State, but the race remains fluid, with many voters having not definitively made up their minds.