Forgive my generalizations, because there's going to be a freak of a lot of them:
The GOP, the underdog, in this race is doing horrible things to one of it's base groups-- the Evangelical Christians. It's odd that they'd already be at a disadvantage (note: it's a rarity in history where a single party will hold both houses of congress AND the presidency-- yes, that's why we talk about the genious of Karl Rove), but they're certainly crippling themselves far worse than they need to be.
The "gay marriage" thing is important, but not election-worthy important to Evangelical voters. Generally, it's the abortion issue that tends to sway such voters in primary elections. The one thing that you have to keep in mind is that the Evangelical-crowd equivocates pro-choice with Satan, so voting democrat is out of the questions. It's just *which* Republican they want to throw their support to.
Giuliani's easily out of it. He's pro-choice and admits it. Every time he's asked about what he'll do about abortion he says "nothing", but will usually point out that even if he was pro-life he couldn't do anything even if he wanted to completely disreguard the constitution (someone better watch out for the Giuliani guy, one of these days he's liable to say something crazy)...
Mitt Romney is a MORMON. The Evangelical crowd isn't going to want to vote Mormon ("they're not real Christians!"-- I blame the education levels). And if that wasn't enough, he used to be pro-choice until a fairly recent election-friendly flip-flop. In attempt to get this out of the way, he went to speak about it and why it makes more sense to be pro-life. This was nothing more than an attempt to get the audience to agree with all the points he makes and therefore get them to like him better.
The Evangelical's both in the polls and the press like Fred Thompson more. But this boring, old, crusty, unattractive heck entered the race far too late and might die out of boringness before too much longer anyway.
The Evangelical's (smarter than they look), realize this and they're trying SO hard... they're trying so, so, so hard to support Romney. Because they want a shot at this presidency thing in '08. But Romney, a mix between JFK and John Kerry makes this a bit hard for them. There's always something about the Romney speeches that seems insincere. Perhaps it's the lack of emotion in his voice, or perhaps it's because he's busy trying to appear "politically correct" (which term from this point on will now be reffered to as "socially acceptable") that he won't tell you much about what he'll actually do other than it'll be conservative and he'll attempt to do it in a way that's appeasing to both Republicans and Democrats. The latest is that he'll appoint judges (if any die while he's in his four year term... a feat I consider to be unlikely) who can overturn Roe v. Wade. I hope no one actually believes this...
(No seriously. Next time you're at Borders, go look up his book on how he won the Olympics and made Utah a success.)
The latest was when Romney said that he's not going to "try and distance [him]self in any way, shape or form from [his] faith". He also added that he wouldn't take input from religious leaders (see: JFK). So he's trying to juggle it all. But he's going to do much better in the primaries than Thompson, so it looks like he's the Evangelical's best bet. Although when Mormanism is being reffered to as "a cult" in the national media, you've got to wonder what they'll end up doing.
P.S. Upon reflection, I need to start giving McCain more credit than I have been. I feel safe enough to say that I don't need to worry about Ron Paul, but McCain started running a DANG good ad that could help him a lot...