By Alex Knott, CQ Staff

It won’t amount to a run on the bank, but you can bet that Sen. Arlen Specter ’s campaign committee will soon be busy refunding a lot of money to disappointed Republicans.

Start with Senate Minority Leader Mitch McConnell , R-Ky., who just donated $10,000 to the Pennsylvania Republican — ah, make that Pennsylvania Democrat — to help him prepare for his 2010 re-election bid.

McConnell hasn’t asked for his money back just yet, given the fact that Specter only announced his defection to the Democratic Party this morning.

But he and others GOP lawmakers who gave Specter a collective $42,000 in March alone, will likely be demanding a speedy refund.

The donations to Specter during the first quarter of this year were significant because political action committees connected to McConnell, Sen. Orrin G. Hatch , R-Utah, and Sen. Richard C. Shelby , R-Ala., gave the maximum of $10,000 each. During the four years prior, senator-connected PACs gave $23,000 to Specter, but he was not gearing up for a re-election bid during those years.

Specter has already signaled his intention to return the money — but only if asked.

“Upon request, I will return campaign contributions contributed during this cycle,” he said in his statement announcing his party switch.

Specter did well during the first quarter, raising $1.2 million, which added to his war chest of $6.7 million. His campaign fund is the fourth-largest among Senate candidates.