During his primary campaign, while Barack Obama concentrated on inspiration, his staff concentrated on arithmetic.

While the Hillary Clinton campaign thought the race was about the big states they won — We won California! We won Massachusetts! We won Ohio! We won Texas! — the Obama campaign knew it was all about the slow, steady accumulation of delegates.

He accumulated more delegates than Clinton, and that was that.

Math was king during the primaries, and I think it is going to be king again when it comes to Obama picking his running mate.

Running mates really don't have that much to do during the campaign — they give speeches that get little press coverage, and they debate each other one time — but you want them to do something on Election Day.

In the case of Obama, I think he wants his running mate to help him with the math. I think he wants his running mate seriously to help him get to 270 Electoral Votes and victory.

Toward that end, I hear two names at the top of his short list are Virginia Gov. Tim Kaine and Indiana Sen. Evan Bayh.

Both have pluses and minuses.

On the minus side for Kaine, I hear the Obama people are wondering if he can really take a punch. Virginia governors can serve only one term, so they never get re-election experience. They don't know what it is like to have to defend their records, as Kaine would have to do as a vice presidential nominee.

On the minus side for Bayh is that he was an early Hillary Clinton supporter, whereas Kaine was an early Obama supporter. Does Obama really want to look disloyal to those who went to bat for him? (On the flip side, however, is that putting Bayh on the ticket could be seen as a way of reaching out to Hillary's supporters and giving them a consolation prize.)

On the plus side for Kaine is Virginia's 13 electoral votes in a Southern state that Democrats would like.

On the plus side for Bayh is Indiana's 11 electoral votes in a state Democrats almost never win. Indiana was one of the two Great Lakes states (Ohio was the other) that Democrats lost in the presidential contest of 2004.

So this becomes the real calculation: Can Obama win Virginia without Kaine on the ticket? Maybe.

But can Obama win Indiana without Bayh on the ticket? Probably not.

So you do the math.

To find out more about Roger Simon, and read features by other Creators Syndicate writers and cartoonists, visit the Creators Syndicate Web page at www.creators.com.

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