I go with zoffenberger's interpretation here; I believe the key to that comic is the "is there even a difference?" line.
This comic is *lame*. Sure, it's a satire of media, but let's not kid ourselves. To those who think this isn't a political statement: may I remind you of this blog entry http://blog.xkcd.com/2008/01/28/obama/ ? Some of the Romney quotes on this one could have been said by Obama or any other politician (e.g. the one on the budget). But the first one for instance is completely different, as abortion is the kind of issues that make you react very strongly and emotionally, it's not "just politics". At first, I thought Munroe was trying to say "give him a break, he's not as horrible a person as you thought he was!", but in fact, taking a quick look at Romney's Wiki article:
In 2005, Romney revealed a change of view regarding abortion, moving from an "unequivocal" pro-choice position expressed during his 2002 campaign to a pro-life one where he opposed Roe v. Wade.
[Romney] later said, "Changing my position was in line with an ongoing struggle that anyone has that is opposed to abortion personally, vehemently opposed to it, and yet says, 'Well, I'll let other people make that decision.' And you say to yourself, but if you believe that you're taking innocent life, it's hard to justify letting other people make that decision."
Either Munroe did his research wrong, and genuinely thinks Romney is pro-abortion (which I highly doubt since I assume his real, current views on this issue have been discussed at length in the American media), or 1) not only is he saying "guys, Romney's anti-abortion! We, as young reasonable progressive people who voted for Obama in '08, should totally despise this guy", he is also 2) calling our attention on Romney's flip-flopping. Oh geez, that's really not partisan at all.
So, no he's not saying explicitly "VOTE OBAMA", but as if it wasn't obvious... ^^; And actually, the fact that he doesn't say it is even worse IMO, it's disguised as a "haha won't you lol, dear reader? INCIDENTALLY, WE'LL SOON HAVE TO CHOOSE OUR PRESIDENT" and as a faux-neutral take on media and politics. Again, there *is* a political statement. Politics have nothing to do in xkcd (I mean, IMO. Of course, the author does what he wants to do), and as has been pointed out, the fact that a lot of people who read it don't even know who Romney is makes it, hey, even worse. Not that it makes it funnier to know who he is. Also, I bet most Americans don't know about the HuffPo thing, and, contrary to, say, the math jokes, you can't actually find out about it only by reading this comic since there's no clue whatsoever that it is a parody of something very specific. The reference is completely lost unless you read it yourself, have a friend tell you about it, or visit this forum. It's a big deal, because the comic doesn't look like a journalistic work; what I mean by that is, I read it with Munroe's voice at first ("I just had this silly idea, and I mixed it with some more serious political views, check it out:"), not as a parody; I can say I didn't get the point until I read the original.
But more importantly, Munroe should seriously stop trying to "educate" his readership on politics, how to treat women, free software, etc. ...at least on politics. Think of those of your readers who don't agree with you: they're reading their xkcd 3 times a week, having fun and all, and then you put up this kind of comic, basically telling them they're asses. Wow, great work, Mr Munroe, you really do care about your fans!
Lastly, the idea of the comic is good IMO. The "is there even a difference?" line is funny and a good satire, and I like how he shows that biased "journalists" can be found on both sides. More generally, it shows how silly the media have become. But he didn't have to use authentic Romney quotes, or even use RL characters, and not-so-subtly remind people to vote for the other guy.
P.S: I'm not American, but if I were, I sure as heck wouldn't vote for Romney, and I like xkcd most of the time. Ah, also, when I start writing there's no stopping me, and unfortunately, I sometimes end up going a bit too far when debating/proposing arguments. I probably won't agree with any of this shit in a couple hours. Heck, in reality, I don't even really care about this comic (still didn't find it a hell of a lot funny) and the political statements that may or may not be included in it haha.