Now that each party has basically chosen its Presidential nominee, the next political milestone is each nominee's choice for the VP slot. The running-mate choice will be seen as more important this year than in most election years -- in McCain's case because of his age, and in Obama's because of his inexperience. I think that the question presents McCain with an opportunity, and Obama with a conundrum.
Let's start with Obama. For whatever reason, it seems that Hillary Clinton is not under consideration (and there are good reasons why she might turn down the VP position if offered). That leaves him with two options: a woman other than Clinton, or a man.
Choosing a man would likely solidify the alienation of feminist Clinton supporters who already believe, with considerable reason, that Clinton was shoved aside in favor of a less worthy candidate due to sexism; the party would be offering "another boringly male Democratic Presidential ticket
". Many of these individuals would never consider voting for Obama regardless, but however many among them are actually wavering would see it as a shut-out.
Choosing a woman other than Clinton presents its own set of problems. Feminists would be likely to interpret it as pandering -- and naive pandering at that, especially if the woman chosen were relatively centrist politically, as in the case of Governor Kathleen Sebelius of Kansas, who is regularly mentioned as a possibility. Moreover, a critical Clinton constituency which Obama needs to win over is blue-collar and rural voters in Appalachia and the Midwest (Rasmussen now shows
McCain leading Obama 46%-40% in Ohio, or a startling 52%-42% if "leaners" are included). These voters were attracted to Clinton not because of her gender, but because she was better able to connect with them on economic issues and culturally than the (perceivedly) more elite, ivory-tower Obama. Choosing a woman running mate, in and of itself, would do nothing to enhance Obama's appeal to this constituency.
There's another factor which is a bit awkward to mention in polite circles, but nevertheless real. History being what it is, the US is used to white male leaders. Everyone recognizes that nominating either a black man or a woman for President would have been revolutionary. A ticket consisting of a black man and
a woman might be, for some people, just a little too much revolution to swallow all at once. The number of people whose votes would actually be swayed by such feelings is probably small, but in an election where a shift of a couple of percentage points one way or the other could decide the outcome, it's a factor which Obama is doubtless considering.
In the end, I think Obama will choose a man as his running mate. Despite the drawback of further disappointing feminists, on the whole the balance of considerations favors it.
Turn we now to McCain. He has the advantage of low expectations -- being viewed as the stodgy, traditional candidate, he's expected to do the "safe" thing and choose one of the more successful of his competitors for the Republican nomination, such as Romney or (please, no!) Huckabee. Thus he has more to gain by making a bold choice.
One such bold choice would be Senator Joe Lieberman. Lieberman would be, as far as I know, the first avowed non-Christian on a major party ticket since the days of the Founders; and a Jewish candidate, unlike a Muslim or Wiccan (or perhaps even a Mormon) would not turn off
any voters outside small groups of cranks and extremists. The bigger factor would be the fact that Lieberman is not a Republican; by reaching outside of his own party, McCain would steal Obama's bipartisan thunder at a stroke. (It's not out of the question, by the way, that Obama would choose a moderate Republican running mate for similar reasons -- though this would make it harder for his followers to keep scolding the PUMAs in the name of party loyalty.) Lieberman also has the advantage of being unquestionably experienced enough for the Presidency.
The other option for a bold move would be to choose a black or woman running mate. Of these, a woman would be by far the more effective at boosting support for McCain. Black voters are a solidly Democratic constituency and would be very unlikely to desert a Democratic ticket headed
by a black man, regardless of who the Republican VP candidate was. But a woman running mate in a race against an all-male Democratic ticket might very well shift enough feminist PUMAs from the "won't vote" to "vote McCain" position to swing a close race. The most commonly-mentioned possibility is Governor Sarah Palin
of Alaska, who at 44 might seem young for the position (though it would be hard for Democrats to make this argument since Obama is only 46), but has the highest approval rating
of any Governor in the US.
(If McCain wanted to make a really
radical move, he'd offer the VP spot to Hillary Clinton. There is, however, almost no chance that she'd accept.)
In the end, of course, voters mostly choose on the basis of the top man on the ticket, not the running mate. Yet the two candidates' choices will tell us much about their calculations.