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.