Somebody recently told me that Barack Obama can’t be elected president because in the past 100 years, only one sitting Senator has won a presidential campaign. Every year, I hear this argument advanced against one candidate or another, and it never makes any sense to me. This year it makes even less sense.

For one thing, 100 years is way too far to go back. In 1907, women couldn’t vote, TV hadn’t been invented yet, and nominees were actually chosen during the party convention. What does that have to do with modern-day America?

Personally, I’d say the earliest you could really go back is 1960, which featured the first televised presidential debate, marking the first time a candidate really had to look good on TV. Since 1960, we’ve had 12 presidential elections. I’m no statistician, but I think most scientists would tell you that 12 elections is way too small a sample to conclude anything useful.

But if you do think you can conclude anything from those 12 elections, then the fact is that Obama has a huge advantage. Why? Because, although only 1 out of every 10 Americans is left-handed, 5 out of 12 presidential elections have been won by a southpaw. Obviously, left-handers have a massive statistical advantage.

And guess which hand Obama writes with?

By the way, if you really think that being a senator means you can’t get elected president, then the winner in 2008 won’t be Barack Obama, Hillary Clinton, John Edwards, John McCain, Joe Biden, or even Sam Brownback. And since being mayor of New York has never launched anybody into the presidency, we have to rule out Rudy Giuliani.

That leaves… Let’s see… For the Democrats, Governor Tom Vilsak, Governor Bill Richardson, General Wesley Clarke, and Rev. Al Sharpton. For the Republicans, it’s one of the following governors: Mitt Romney, John Gilmore, Mike Huckabee, or Tommy Thompson. (Unless the Republicans nominate one of their two candidates who have never held elected office: radio talk show host John Cox, or Hewlett Packard engineer Michael Charles Smith.)

Some of these are plausible choices, I guess. It’s conceivable that a former governor could end up heading one or both tickets. But at this early stage, the most likely possibility is that both tickets will be headed by a Senator.