I think the GOP simply guaranteed it to him. Look at the following evidence:
The primary season began early so the RNC wouldn't be wasting a lot of time and money. They also had more than enough cash to spare anyway and there were probably advantages to having phony primaries/caucuses.
All of the fraud was in favor of Romney at the expense of both Santorum and Dr. Paul, but mostly the latter (in particular, the vote flipping done by machines).
Romney dropped out in 08 when he still had a chance against McCain (Romney was considered the "conservative" candidate in 08). Romney likely would've won the nomination in 08 if he had stayed in, but he knew he couldn't beat Obama then. Why would he have dropped out if he could've beat McCain?
The campaigns of Michele Bachmann, Cain, and Perry.
There are no guarantees from the Establishment but, yes, I think they probably tapped him early on for the '12 nomination. One of the things people don't realize is that the Establishment has to run a "credible threat" against the incumbent as part of the dog-leash that keeps the incumbent following orders. If Obama were to find himself running against an easily defeated candidate, he might begin to have delusions of grandeur and start thinking he can actually make his own decisions without consulting his superiors. And that's not good. So, the Establishment really wants every election to be a 49/51 where they can easily manipulate the spread to punish or reward the incumbent according to how faithfully he follows orders.
Clayton -
That's why the establishment Republicans viciously attacked Herman Cain - they couldn't control him. He wasn't perfect, but I at least felt he was open to learning what the real problems are, e.g. audit of the Fed. I liked his business background, problem-solving abilities, and apparently genuine good nature.
You could say the same about Perry, but he's fallen back in line with supporting lousy David Dewhurst.
Romney will be complicit with the terrible Republican establishment. They set up John McShame as the 2008 fall guy.
Clayton,
You think Romney is a credible threat to Obama and I know that he went to Bilderberg this year (which has a history of inviting the winner, not just the nominee), but I don't see how Romney can attack Obama in the debates.
I think the Establishment wants Romney to win due to the Iran issue. Obama's ilk don't have a history of supporting Israel and Romney and the GOP do. Either just before the election or just after...