Richardson's main problem is his tendency to stick his foot in his mouth all the time, making him a really bad campaigner. He also supported the war initially, which undermines Obama's message of being opposed to the war from the start.

It's possible that his appeal to Latino voters would outweigh any of those disadvantages, but it's hard to say. There's also the issue of having no white guys on the ticket at all, which should not be discounted. It's one thing to say that Democrats will never win in the deep South, but having a ticket with no white guys on it is going to have an effect in purple and blue states as well, especially with McCain's fake moderate credentials and appeal among his fellow AARP members.

If Hillary ends her campaign soon and numbers come out saying McCain is beating Obama head-to-head among Latinos (certainly a possibility given McCain's position on immigration issues) then maybe it's time to start thinking about Richardson as VP, or perhaps announcing that he'd be Obama's pick for Secretary of State or something. But I think there are other VP choices that would be more appealing to a wider segment of the population, and that's usually how campaigns pick their running mates.