Sen. John McCain's chief campaign aides suddenly resigned this morning, leaving no explanation for their departure. John Weaver, McCain's longtime strategist, and Terry Nelson, his campaign manager, released short statements announcing they were leaving the campaign effective immediately.

The news shocked McCain's allies and was especially surprising in light of last week's campaign redesign, which was orchestrated by Weaver and Nelson.

Nelson's statement reads:

"This morning I informed Senator McCain that I would be resigning from his presidential campaign, effective immediately. 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."

Here is Weaver's statement:

"As of today, I have resigned my position as chief strategist to John McCain's presidential campaign. It has been my honor and a distinct privilege to serve someone who has always put our country first. 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."