The most obvious factor militating against runs by these Democratic power players is their age. Biden would turn 74 right after Election Day 2016, and Clinton would turn 69 just before it. Both of them may have other things they want to do with their lives before it’s too late. Clinton, for instance, has made no secret of her yen for a grandchild. And she and her husband are reportedly hunting for a vacation home in the Hamptons, suggesting she has a slower pace in mind. …

Which leads to the next reason neither Biden nor Clinton will run. Their reputations will never be better than they are now.

Biden’s two failed presidential runs did nothing to enhance his place in history–in fact, the opposite. Even during the 2012 campaign, it seemed that for every great line (“Bin Laden is dead, General Motors is alive”) there was a gaffe (his crack to a mostly black audience that GOP plans to deregulate Wall Street would “put y’all back in chains”). Remarks that seem funny and charming now might not play so well on the presidential campaign trail (“Spread your legs, you’re going to be frisked”). …

Biden and Clinton are household names in American politics, and each would have an advantage in a multicandidate primary field. Yet in a general election, their stature as battle-tested veterans could make either of them seem like yesterday’s nominee against one of the fresher, younger figures on the Republican bench.