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The billionaire financier Stanley F. Druckenmiller has signed on to support Gov. John Kasich presidential bid, the Kasich campaign said on Sunday.

The campaign pointed to Mr. Druckenmiller’s support as a sign of confidence in Mr. Kasich’s viability in the Republican field, despite the Ohio governor’s fifth-place finish in the South Carolina primary on Saturday and the challenging path that lies ahead of him.

“There’s a good number of donors who recognize the importance of having a governor in the race, and recognize that Kasich’s path is just as strong as any of the senators,” Chris Schrimpf, a spokesman for Mr. Kasich, said.

Mr. Druckenmiller confirmed in an email that he was supporting Mr. Kasich, but did not elaborate. Last year, he donated more than $450,000 to groups supporting Mr. Kasich, Gov. Chris Christie of New Jersey and former Gov. Jeb Bush of Florida.

Mr. Kasich also recently won over Kenneth G. Langone, the billionaire co-founder of Home Depot who had been a leading supporter of Mr. Christie.

Fund-raising is a major looming challenge for Mr. Kasich if he is to remain in the race for the long haul. At the end of January, Mr. Kasich’s campaign had only about $1.5 million on hand, though his chief strategist said on Saturday that fund-raising had increased significantly after Mr. Kasich’s second-place showing in the New Hampshire primary.