The Hagel Effect
I don't puch much stock in "electability" arguments for chosing candidates in a primary. I won't make an electability argument about any of the candidates currently in the running. At this point, I don't see any of the top four or five Dems in the field--Clark, Clinton, Obama, Edwards, Richardson--losing to any of the Republicans currently in the field. (I include Clark because he hasn't said he isn't going to run and there is still some time. Also, he's my top choice.) I say that in all seriousness. McCain went from "straight-talk express" (I never bought it) to "say anything depending on the audience". The real Rudy Giuliani won't be as popular as the mythical 9/11 "Mayor" is--just ask New Yorkers. I don't think the others really stand a chance with moderates.
That said, I think they dynamic changes a lot if Chuck Hagel throws his hat in the ring. When it comes to foreign policy, Hagel is everything that the "straight-talk express" isn't. Namely, a straight talker. He's probably one of the most conservative members of Congress (voting AGAINST the minimum wage increase!), but he's not portrayed as extreme as, say, a Brownback. A Hagel presidency will probably see Roe overturned by his supreme court pick as well as a host of other very important principles of American jurisprudence. But you won't likely hear much about that. Instead, you'll hear about his domestic "moderation" (a lie) and his respect in foreign policy circles. (Even I respect what he says.)
If Hagel is in the race, the Democratic nominee will be someone perceived, rightly or wrongly, as a moderate domestically and a strong national security candidate. That does not bode well for the current top three. I think Edwards and Obama would be particularly crippled by a Hagel run. They may say the right things and pursue the right policies (which I think they will), but to many you'd be taking a risk with them. To a lesser extent, Clinton is succeptible. I think Clinton is a contender no matter what and has a great campaign team, but will have a tough time with Hagel.
The Dems who will most easily be able to fend off a Hagel challenge on foreign policy credentials are Clark, Richardson and Biden. Listening to Hagel talk now is like listening to Clark from three years ago. (In fact, a lot of the FP establishment is starting to repeat Clark's advice.) Clark has already won a war and is well respected internationally--which other candidates are invited to speak at middle east economic development conferences or testify at the Hague? Similarly, Richardson has been ahead of the curve as well and is very much respected internationally. He's called to negotiate for prisoner release and has dealt with N. Korea in nuclear negotiations. He's ready to go. Biden can go toe-to-toe with Hagel and has always been a step ahead of Hagel in realizing the dangerousness of the Bush administration.
I prefer Hagel as the GOP nominee because I think he may be less sleazy than the other GOP candidates on the campaign trail. However, that will make it much tougher for any Democrat to win. I do think Dems can win, but we'd have a much easier time if Clark or Richardson were the nominee--and I'd like to be lazy this time.
I have to admit that I also find Clark and Richardson to be the candidates with the most pertinent experience and the most qualified.