The WaPo has the story:
John Dowd represented Sen. John McCain in his darkest hour, the “Keating Five” scandal. He supported McCain the first time he ran for president in 2000 and signed up to be a major fundraiser for him in this year’s presidential race. But when former senator Fred D. Thompson began thinking about running, the Washington lawyer changed his mind.
For McCain (Ariz.), who started off as the favorite to win the Republican nomination but now trails former New York mayor Rudolph W. Giuliani in most polls, Dowd’s move signals yet another threat to his struggling campaign. As Thompson (Tenn.) builds his team of major fundraisers such as Dowd, the challenge for McCain will be to collect the millions of dollars necessary to maintain a nationwide campaign and convince Republicans that he is their best bet to retain the White House.
“I am very sorry to see what’s happened to John,” Dowd said in an interview. “I don’t think his campaign is being well run. It’s been over-managed. He blew through $8 1/2 million. It’s a difficult thing to leave a friend and go to another friend. But we lost the John McCain I knew.”