Ann Althouse, a self-proclaimed political moderate, compares and contrasts discourse on the left and the right:

I'm just saying that I'm struck by the way the right perceives me as a potential ally and uses positive reinforcement and the left doesn't see me as anything but an opponent -- doesn't even try to engage me with reasoned argument. Maybe the left feels beleaguered these days, but how do they expect to make any progress if they don't see the ways they can include the people in the middle? If you look around and only see opponents and curl up with your little group of insiders, you are putting your efforts into insuring that you remain a political minority.

Or as Glenn Reynolds wrote a few years ago:

As the old saying has it, the left looks for heretics and the right looks for converts, and both find what they're looking for. The effect is no doubt subliminal, but people who treat you like crap are, over time, less persuasive than people who don't. If people on the Left are so unhappy about how many former allies are changing their views, perhaps they should examine how those allies are treated.

Indeed^TM.

Update: Steve Green, a "Falwell-tweaking, gay-marriage supporting, drug legalizing, pro-abortion, pro-immigration, anti-trade barrier, wary-of-organized-religion kind of guy" adds:

The right seems to love a good debate, and the left seems to love pissing on them for it.

Which is too bad. Jonah Goldberg recently wrote:

If liberals really want to emulate conservative successes, I have some advice for them: Get into some big, honking arguments — not with conservatives, but with each other. The history of the conservative movement's successes has been the history of intellectual donnybrooks, between libertarians and traditionalists, hawks and isolationists, so-called neocons and so-called paleocons, less-filling versus tastes great. Liberals would be smart to copy that and stop worrying how to mimic our direct mail strategies.

Liberals have a tendency to mistake political tactics for political principles, and vice versa. Exhibit A is the Left's fascination with "unity." Unity is often useful in politics, but it's often a handicap if you haven't figured out what to be unified about. Just as the Socratic method leads to wisdom, big fights not only illuminate big ideas, but they force people to become invested in them. Unfortunately, liberals define diversity by skin color and sex, not by ideas, which makes it difficult to have really good arguments.

Of course there are arguments on the Left and there are individual liberals with deep-seated convictions and principles. But most of the arguments are about how to "build a movement" or how to win elections, not about what liberalism is. Even the "Get out of Iraq now!" demands from the base of the Democratic party aren't grounded in anything like a coherent foreign policy. Ten years ago liberals championed nation-building. Now they call it imperialism because George W. Bush is doing it.

* * *

Bill Clinton was the only Democratic president elected to two terms since Franklin Roosevelt. One of the reasons for his success was that he was willing to pick fights with his own party. One can argue about the sincerity of some of those fights. But we remember the Sista Souljah moment for a reason.

A big reason why there's so much Nostalgie De La Left is that so much of liberalism seems to be stuck reliving its glory days, something Mark Steyn observed on Thursday:

things like the King funeral are such a tragedy for [Democrats], because you realize that they're...all that is important to them are the battles they won thirty and forty years ago. And the battles that need to be fought now, they're making no contribution to.

Nobody knows what's going to happen in November, but if the result, as Steve recently predicted, is further self-immolation by the left, I'm of two minds. On the one hand (my right hand, I guess), I'm not going to lose any sleep over the left going off a cliff. But on the other, I'd like to see them return closer to the center. I realize we'll never have a presidential election with candidates as closely united on the big issues of the day as we did in 1960. And as much as Jonah is correct that infighting amongst the members of a party is healthy, vigorous debate between parties is equally useful. But part of me does (rather naively, I know) wish the chasm between the right and the left wasn't as enormous as it is now.

A year ago, Michael Barone famously wrote, "The left blogosphere has moved the Democrats off to the left". If that's true--and by all evidence, it's dead-on--then don't expect momentum to shift from the left back to the center anytime soon.

And that's a prediction I'd be very happy to be wrong about.