• Pennsylvania Lt. Gov. John Fetterman raised $1.6 million in the 24 hours that followed his Democratic Senate primary win, Fetterman's campaign said.
• Fetterman suffered a stroke last week that kept him off the campaign trail in the final days of the primary.
• Fetterman will face off in the general election against the winner of the Republican Senate primary, which could be ex-hedge funder Dave McCormick or Trump-endorsed celebrity Dr. Mehmet Oz.

Pennsylvania Lt. Gov. John Fetterman raised $1.6 million in just 24 hours after winning the Democratic primary to compete for the state's all-important open U.S. Senate seat, his campaign said Thursday.

Fetterman, 52, raked in those donations after suffering a stroke last week that kept him off the campaign trail in the final days of the primary. He underwent a successful pacemaker surgery Tuesday, the day of the election.

"Thank you, from the bottom of my heart, for your support," Fetterman said Thursday through his campaign. "I am deeply honored to be your nominee, and I am looking forward to turning this seat blue in November." 

The Fetterman campaign did not immediately respond to CNBC's request for further detail about the donations.

Fetterman will face off in the general election against the winner of the Republican Senate primary, which has yet to produce a nominee.

The top contenders, ex-hedge funder Dave McCormick and Trump-endorsed celebrity Dr. Mehmet Oz, are locked in a neck-and-neck race that appears to be headed toward a recount. The two candidates' campaigns have each predicted that they will emerge victorious.

The progressive Fetterman's laid-back style and populist politics endeared him to Pennsylvania Democrats: Fetterman won every county in the state, NBC News projected.

He defeated his nearest rival in the primary, U.S. Rep. Conor Lamb, by nearly 33 percentage points, according to NBC.

Fetterman's campaign had nearly $1.87 million cash on hand as of late April, according to the most recent Federal Election Commission filings. Fetterman had raised more than $16 million in total as of April 27, FEC data shows.

The race to fill the seat being vacated by GOP Sen. Pat Toomey could prove to be one of the most important fights of the midterms. Democrats are trying not to lose control of the Senate, which is evenly split between 50 Republicans and the 50 senators who caucus with Democrats — while Vice President Kamala Harris holds a tiebreaking vote.

The Pennsylvania Senate race may offer Democrats' best chance to flip a red seat blue.

The party quickly got behind Fetterman. In a statement Tuesday night, President Joe Biden said that the Democrats are "united around John."

Fetterman "understands that working class families in Pennsylvania and across the country have been dealt out for far too long," Biden's statement said. "It's time to deal them back in, and electing John to the United States Senate would be a big step forward for Pennsylvania's working people."