“This morning I informed Senator McCain that I would be resigning from his presidential campaign, effective immediately,” said Nelson, who served as campaign manager. “It has been a tremendous honor to serve Senator McCain and work on his campaign. I believe John McCain is the most experienced and prepared candidate to represent the Republican Party and defeat the Democratic nominee next year.”

John Weaver, McCain’s chief strategist, also resigned.

“It has been my honor and a distinct privilege to serve someone who has always put our country first,” he said. “I believe that most Americans will come to the conclusion that I have long known there is only one person equipped to serve as our nation's chief executive and deal with the challenges we face, and that person is John McCain.”