Option three. McCain really was the best candidate the GOP had. Considering how badly he was ravaged in the campaign, imagine what would have happened to Romney or Huckabee.
That was the CW back then. But it can be debatable now.
For all his cons, Romney wouldn't have been drowned by Obama's money machine. He could speak with authority about the economy, even while the Democrats would criticise him for his CEO past.
He would have run a much more organised and disciplined campaign. And of course he wouldn't have botched so badly his vice-presidential choice.
Same with Huckabee. He would have mobilised the religious base, while at the same time he was still a likable figure for everyone else. And his populist rhetoric would allow him to denounce the bailout and Wall Street more forcefully and convincingly than McCain (not to mention of course that he wouldn't be burdened by the vote for it), thus hitting Obama from the left on the economic front.
I think that both of them would have started way more behind than were McCain started his GE campaign last March. But in the end they would have ended with pretty much the same votes like him.
I think that Romney would have been obliterated due to appearing too corporate, so to speak (especially after the credit crunch). My opinion of him as improved a lot since then though, so I'm not so sure of that anymore.
Huckabee's likability could only carry him so far. We saw in the primaries that it carried him to victory in Iowa. Once people learned what his views were like things started to change.