Sen. Bernie Sanders Bernie SandersNYT editorial board remembers Ginsburg: She 'will forever have two legacies' Two GOP governors urge Republicans to hold off on Supreme Court nominee Sanders knocks McConnell: He's going against Ginsburg's 'dying wishes' MORE’s (I-Vt.) campaign said Wednesday it raised more than $1.3 million in one day in response to a super PAC’s negative ad targeting the senator over the heart attack he suffered last year.

The presidential candidate received more than 70,000 donations the day after his campaign warned supporters about an ad from the Democratic Majority for Israel scheduled to begin airing Wednesday, The New York Times reported. The PAC's president, Mark Mellman, is an opinion contributor for The Hill.

The super PAC launched the almost $700,000 ad campaign in the days before the Iowa caucuses. The ad highlights voters characterizing Sanders as too uncertain, as a left-wing progressive, in his ability to beat President Trump Donald John TrumpBiden leads Trump by 36 points nationally among Latinos: poll Trump dismisses climate change role in fires, says Newsom needs to manage forest better Jimmy Kimmel hits Trump for rallies while hosting Emmy Awards MORE, with one voter also mentioning his heart attack earlier in the campaign and their concerns about the senator’s health.

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Sanders’s campaign manager Faiz Shakir said in a statement obtained by the Times that all Democratic presidential candidates should denounce “negative attack ads run by dark money groups.”

“But what our ​fund-raising ​numbers show is our supporters know the establishment will do anything to try to stop Bernie, and they’re ready to rally to his side at a moment’s notice,” he said.

An official from the Sanders campaign deferred to the Times article for comment.

Sanders and former Vice President Joe Biden Joe BidenBiden leads Trump by 36 points nationally among Latinos: poll GOP set to release controversial Biden report Can Donald Trump maintain new momentum until this November? MORE are in a tight race in the Hawkeye State, with former South Bend, Ind., Mayor Pete Buttigieg Pete ButtigiegBipartisan praise pours in after Ginsburg's death Bogeymen of the far left deserve a place in any Biden administration Overnight Defense: Woodward book causes new firestorm | Book says Trump lashed out at generals, told Woodward about secret weapons system | US withdrawing thousands of troops from Iraq MORE and Sen. Elizabeth Warren Elizabeth WarrenGOP set to release controversial Biden report Biden's fiscal program: What is the likely market impact? Warren, Schumer introduce plan for next president to cancel ,000 in student debt MORE (D-Mass.) right up there with them.