Weird that McCain's overall favorables were almost the same in the population at large as they were among just conservatives.
Before the 2008 campaign, McCain was about as popular among Dems and Independents as he was Republicans.....presumably because he spent so much of his time in the early 2000s on issues where he sided more with the Dems than the GOP (Bush tax cuts, patients' "bill of rights", campaign finance reform, climate change, immigration....). Here's a March 2006 poll in which McCain has majority favorable ratings from across the ideological spectrum:
http://abcnews.go.com/Politics/PollVault/story?id=1694406