Bunning is behind in fundraising, Politico reports. His most recent financial report, from September, said that he had $175,000 in his campaign account, while other Republicans facing 2010 campaigns have at least four times as much.
Senate Minority Leader Mitch McConnell, R-Ky., spent $21 million in his last campaign.
"They don't have the fundraising guns to understand how difficult a fundraising climate they're in," a Kentucky operative said of Bunning's political staff. "It's going to be a nightmare,"
Bunning himself shows no sign that he is ready to step down.
"It's a free country," he said in a statement. "Anybody can run for anything they choose. I am gearing up, and I look forward to the challenge of taking on whoever comes out of the Democrat primary in May of 2010."
Bunning, a Hall of Fame pitcher with the Tigers, Dodgers and Phillies, served in the House from 1987 to 1999. He won close races in 1998 and 2004 to the Senate.
Notable deaths of 2014 [PHOTOS]