Sen. John McCain's reputation as a maverick who regularly bucks the conservative wing of his party will be a formidable obstacle for Sen. Barack Obama as he seeks to persuade moderates to vote for him in November.

There were moments when John McCain had no idea if his friend even knew he was there. For eight long years, at least once a month, McCain would drive to the veterans' hospital in Washington, D.C., to sit for hours at the bedside of his political mentor, Morris Udall...