(CNN) - Andy Card confirmed in a telephone interview with CNN late Friday he has decided not to run for the seat of the late Sen. Edward Kennedy, and is encouraging state Sen. Scott Brown to run instead.
"I had done my due diligence and decided it was probably not in my best interest to run," said Card, former chief of staff in the Bush White House. "I'm disappointed but not unhappy."
Card said he was "overwhelmed with gratitude from people" e-mailing and calling to urge him to run.
He said it was a "tough, tough decision" and family considerations were a "big part of it" - Card's wife is a minister in northern Virginia, and a campaign would have had him spending so much time in Massachusetts.
Card, who was chief of staff on 9/11, said he only made the decision late today after "I finished my 9/11 remembrance events." He explained he did not want anyone to think his appearances today were in any way political in the event he chose to run.