That's an interesting point, but it begs the question: why not just support McCain?
Why not McCain, when when the biggest negative McCain has is one he shares with Thompson, as you mentioned? Thompson was so important to campaign finance reform that he has actually been given credit for its passage:
Now THAT will leave a mark.
That's not my biggest problem with John McCain. It's just one of them. The biggest is that he is a bit "nutty", he doesn't seem to have the temperament to be President. He also had the gang of 14, and amnesty, and his opposition to reasonable interrogations, and other positions on the war on terror that are off-putting.
That said, I still rank McCain above Rudy, and if I decided not to vote for McCain in the general election it would be because I was so afraid he'd go nuts that I'd rather trust a democrat. Not likely to happen, but it is a real fear I have with McCain. If I have it, I've got to figure he'd have trouble winning the election.
I also find McCain to be very opportunistic, while Thompson's political life doesn't look like one which had votes based on gaining political advantage.
I'm no way sold on Thompson, we don't know nearly enough about him to sell me on him. But he seems intriguing, he certainly seems like he'd have the name recognition, he's got a pretty conservative record, he supports the war, and he's well-spoken and electable.
Of course, I still believe Romney is acceptable, something my fellow conservatives don't agree with me about.
Thompson is like McCain was about 10 years ago when most people still liked him.
And Fred's not a lunatic, either.