Senator McCain is pretty conservative on a lot of issues. However, he is wobbly on several very important (to me, at least) issues.
1. He is against the First Amendment (see "Bipartisan Campaign Finance Reform Act," aka McCain-Feingold).
2. He wants to "close the gun show loophole," which will lead to the elimination of private gun sales.
3. He was co-sponsor of legislation granting amnesty to illegal aliens, which is doubly irritating since he is a senator from Arizona.
4. He wants to continue the current less-than-intelligent prosecution of a perpetual, multiple-fronted "war on terrorism."
Only in the latter of these four issues does he differ from Senator Clinton and Obama, though of course both of them would likely go much further on gun control. Sen. McCain would probably wait until his second term (assuming he got one and wasn't dead or senile) to pursue a serious gun control agenda.
Mr. Giuliani will drop out of the race and endorse Senator McCain. Mr. Huckabee showed rather poorly in Florida, and has no money. Rep. Paul only garnered 3% of the vote in Florida, and never had a chance of gaining the nomination anyway.
That leaves Senator McCain and Mr. Romney. The latter is very suspect on gun control, though slightly better than McCain on immigration, and has flip-flopped on a bunch of issues after he "saw the conservative light" (read: decided to run for national office). However, he claims to oppose McCain-Feingold, which is a good thing if he is being truthful. His position on the war is basically the same as Senator McCain's, though both are better than the present administration's, at least as I see it.
Senator McCain has a lot of momentum going into Super Tuesday, and I'm not sure there's much real difference between he and Mr. Romney, anyway. I don't think I can be persuaded to vote for either of them. I didn't even bother to request a primary ballot for Super Tuesday, and if it's McCain versus Clinton or Obama, I will probably just abstain in the general election or vote for some wacky third party.