Grandmother-in-Chief to be? Photographer: Brendan Smialowski/AFP/Getty Images
Grandmother-in-Chief to be? Photographer: Brendan Smialowski/AFP/Getty Images

Hillary Clinton's age wouldn't keep me from voting for her. She'll be 69 on Election Day 2016. I voted for a 72-year-old by the name of John McCain in 2008.

Age was a legitimate issue to consider when McCain ran for president. (I wrote an article urging him to allay concerns about his age by pledging to serve one term and picking a reassuring running mate. His campaign let me know my advice was considered, but he went a different way.)

It's a legitimate issue to raise about Clinton, too -- and the evidence of recent elections suggests it may well undermine her in 2016.

Americans have not often reached back a generation to choose a president. They've chosen a president more than five years older than the previous one only four times, and Clinton is 14 years older than President Barack Obama. In the four elections with a significant age gap between the party nominees since the Cold War ended, the younger candidate has won every time.

In two of those elections, the age gap was big enough that exit polls asked about it. In 1996, Bob Dole, then 73, lost to a 50-year-old Bill Clinton. In 2008, McCain lost to Obama. Although Democrats went after the Republican's age each time, the polls found that most voters didn't care about the issue. In 1996, in polls asking whether Dole's age affected his ability, 64 percent of voters said no. In 2008, the pollsters were more delicate, asking if the age of the candidates had been a factor in the ballot booth. This time, 60 percent of voters said no.

The ones who did care about age, though, cared a lot. Of voters who thought Dole's age affected him, 79 percent opposed him. McCain lost 66 percent of the voters who said age influenced their decisions. A naive reading of the polls would suggest that age was what cost the Republicans both elections. The people who weren't worried about age gave Dole 58 percent of their votes and McCain 55 percent.

Those numbers are misleading, though, because some voters see age through a partisan filter. Some of the Democrats who said they opposed Dole because of his age, in other words, would've found a different reason to oppose him if he had been younger. And some of the Republicans who professed not to care about his age would have said that a 73-year-old Democrat was too old for the White House.

Two Stanford University professors, Herbert Abrams and Richard Brody, looked at the polling on Dole's age throughout the 1996 race and attempted to control for such partisan sentiments. Their conclusion was "unequivocal": Dole's age did indeed hurt him.

An older candidate, or that candidate's supporters, can try to dismiss concerns about age as mere bias. But the data suggests the limits of that strategy. In 1996, the polls consistently showed that "the older the voter, the more likely he was to believe that Dole's age would be an obstacle," as Abrams and Brody wrote. Their theory: "Older Americans did indeed project on Dole their own experience with health and the problems of aging."

One might have thought that the aging of the electorate would make it easier for an older candidate to win. It may actually have the opposite effect.

The main point of the professors' paper is that voters and the media paid too little attention to the risks of a senior-citizen president. The majority who said Dole's age didn't matter "were simply unaware that the man they might vote for had a 20 percent chance of dying in office or, if they were, they didn't care."

Average out the voters' views, though, and you get a pretty reasonable approach: Advanced age, especially when combined with known health issues, should be a mark against a candidate -- but it shouldn't overwhelm everything else.

And probabilities are just that. Dole picked Jack Kemp as his running mate in 1996 in part because of his vigorous image (he had been a football player). Kemp died in 2009, while Dole is still going strong.

To contact the writer of this article: Ramesh Ponnuru at rponnuru@bloomberg.net.

To contact the editor responsible for this column: Timothy Lavin at tlavin1@bloomberg.net.