[QUOTE=pauliec;2653057]A credible agent of "change" who does nothing to shore up perceived weaknesses.
Sounds like a bull**** VP candidate.[/QUOTE]
A lot of times picking a veep to shore up a perceived weakness simply has the effect of reminding people of the perceived weakness.
One reason Lieberman wound up being a bad choice for Gore was that, as soon as the original excitement over having a Jew on the ticket faded, all the stories about him said "he picked the most pious guy he could find to distance himself for Clinton." The result was it drew extra attention to the weakness.
If McCain were to pick somebody really young, like Bobby Jindal, the result would be: "Look how old McCain looks next to that guy."
The other benefit of picking someone relatively unknown is that you get to dictate the early coverage of the choice. The first few waves of stories will be highly biographical and, by connection, very flattering. If it is Kaine, you'll hear over and over about his appeal within a red state, his religiosity, etc...
If you pick a more nationally known figure, it's harder to dictate the coverage, because the media already has narratives for the choice. Joe Biden --who might be a good choice anyhow-- wouold bring a lot of stories about his plagiarism slip up in the 1980s.
Should McCain pick Romney, for instance, it'll bring alot of coverage about what a douche he was in the primary and all the nasty things he and McCain said about each other. Same thing if Obama were to pick Clinton.
All that aside, the veep tends not to have that big an impact on the result in most years. And one thing that's striking about Kaine is that he's far less charismatic than Obama, so it's almost like he's being picked in part because he won't overshadow the candidate.
If he gets picked at all, that is.