I don't like McCain either, and he would never be my #1 choice for president, but what if he was Romney's VP? Romney would sweep up the Northeast and with McCain on board we might even win California? Too crazy?
As someone said earlier: "that's crazy talk!"
Nobody at 70 years old is interested in being a Vice President.
The core conservative base (the people who actually vote in pubby primaries) will never vote for McCain. There is no point in offering the number two spot to because McCain can't deliver any specific demographic in any appreciable numbers to bother with.
Romney's spineless and will be a "lousy push-over, give the dems what they want and let's make nice" president. The dems will ride him hard and put him away wet. Not what I want in a president. No Thank You.