Roy Bailey, who was a national finance co-chairman for Mr. Perry, said most of the Texas governor’s wealthy supporters would hesitate to back Mr. Gingrich. “The problem is you want to feel the person you’re supporting has a really good chance of succeeding,” Mr. Bailey said. “I think bundlers are waiting to see who emerges to be the conservative choice. Is it going to be Gingrich or is it going to be Santorum? Santorum clearly has a lot of momentum right now.”…

These are the “access” fund-raisers who want a connection to the candidate once he is in the White House, and they commit only to someone with good odds of being the nominee, Mr. Nehring said. “Everybody wants to be an ambassador. You only get to be an ambassador if your guy wins.”

Mr. Gingrich has put little effort into building a network of fund-raisers, focusing instead on the debates. After his one primary victory to date, in South Carolina, the campaign announced that it had quickly raised $2 million in an Internet appeal. But that small-donor momentum has now shifted to Mr. Santorum, whose campaign said it raised $3 million in as many days after his trifecta of victories last week.