Taking on Johnathan Cohn on his own terrain (and I think Cohn's emphasis on presidential ability rather than short-term political tactics is sound), Brad Plumer makes a case for Sebelius as VP pick. This is the bottom line:
Sebelius's biggest strength is the fact that she's the most competent executive of any of the rumored Democratic veep candidates, save for possibly former Virginia governor Mark Warner (whom the Democrats need to win a Senate seat anyway). The fact that, as governor, she erased a $1.1 billion budget deficit in her first year of office without raising taxes, and later steered a large education-funding package through a fractious legislature, would suggest that she's perfectly capable of heading up the executive branch--and doing it well.
There just aren't a lot of people with both executive and foreign policy experience,and the person who best fits that profile (Richardson) has other weaknesses. The other thing to add is that I don't think her less-than-inspiring State of the Union response should be much of an issue. Most people look bad giving them, and if making a dreary entrance on the national stage was a disqualifying factor the Dems would have been stuck with Paul Tsongas in 1992.
--Scott Lemieux