Former Massachusetts Gov. Mitt Romney -- who is trying to position himself as the conservative choice in the race -- was quick to announce Craig's resignation as the Senate liaison to his campaign, and called Craig's actions "disgusting."
Sen. John McCain and former Arkansas Gov. Mike Huckabee publicly urged Craig to resign.
Craig told reporters that he was stepping down so as not to become "an unfair distraction" -- since he plans to continue to fight to clear his name. He has retained a lawyer, and said he plans to try to reverse his guilty plea.
"I have little control over what people choose to believe, but clearing my name is important to me and my family," he said.
His fellow Republicans just hope he keeps it out of the headlines -- at least for the next 14 months.
ABC News' David Kerley, Liz Marlantes and Michael S. James contributed to this report.