If the John McCain of 2000 were running, I’d probably be for him.
But since then, it’s been campaign finance reform, the Gang of 14, immigration reform, etc.
In a general election, McCain may attract independent voters but he’ll also not exactly enthuse the conservative base to get out and vote for him.
If Obama is in the race, there will be lots of new voters.
Don’t forget since 2000, McCain had talks with Kerry in ‘04 about possibly becoming his VP.