I have a theory. It’s half-baked — at best. It’s ill-informed. And, I suspect, it’s not particularly novel. Intrigued? Not really? Oh. Well. That’s understandable. But here it is anyway: the Clintons are most effective when they have aggressive enemies. When they’re not playing offense, in other words, but have their backs to the wall. If I’m right about this, Barack Obama is pretty clearly the wrong opponent for them.

Looking back at the 90s, I remember Bill Clinton being at his best when he was on the defensive. And, more important than that, I think he was blessed with excellent enemies, a rogue’s gallery of rabid idealogues that included Newt Gingrich, Henry Hyde, Ken Starr, and a cast of thousands of wingnut extremists. Nearly every time one of them attacked, I recall Clinton getting the better of the exchange. Usually not with a knockout, but on points. He’d outlast his foe, who always ended up looking like a nutjob, a jerk, a buffoon, or some combination of the three.

Because they were. They were so obviously engaged in partisan witch-hunts that fair-minded observers couldn’t help but side with Clinton. Sure, he was an incorrigible cad and a serial liar. But he was also very good at running the country. And, compared to the ridiculous clowns trying to take him down, he was fantastic.

Coming out of Iowa, the same was true for Hillary. With Chris Matthews bullying her, and John Edwards getting in touch with his inner misogynist, their attacks transformed Hillary into a sympathetic wonk, a technocrat with a heart of gold. She could play defense because the right enemies had made her look relatively good.

For the past two weeks, though, the Clintons have been going for the jugular. And it hasn’t been pretty. I’ve already explained repeatedly why I think they’re making a mistake. But now it seems like the voters in South Carolina shared my concerns. At the same time, the basic rationale for Obama’s campaign — he’s a transformative candidate, who’ll bring thousands of new voters to the polls — has been borne out in the results. And, there no longer seems to be any rationale for Hillary’s candidacy, which used to be predicated on her inevitability. This all adds up to bad news for the Clintons. Worse still, coming out swinging tomorrow might not be an option. Wishful thinking? Probably. But allow me one night to dream my fanciful dreams.

All of that said, I’m not making predictions. The Clinton machine is so powerful, and Bill and Hillary so good at the game, that it’s awesome to behold. Bill, especially, loves getting dirty, even if he pretends otherwise (Did you see this gem? Or, for the campaign more broadly, this one?). Maybe, as the previous two links suggest, their southern strategy, deployed in South Carolina, was all about painting Obama as a race man, diminishing his stature in more delegate-rich states to come. I don’t know. So I’ll still call Hillary the favorite. But I think tonight was big for Obama. And I wonder if a 30-point win suggests that, among other things, he’s a tougher opponent for her than she is for him. Because his cool exposes her weaknesses. While she may have to play to his strengths. And against her own.