Hillary Clinton is 14 years older than Barack Obama. A party has never nominated a leader that much older than his immediate predecessor. (The previous record-holder was James Buchanan, 13 years older than Franklin Pierce when the Democrats chose him in 1856. Runner-up: Dwight Eisenhower, 12 years older than his predecessor, Thomas Dewey.)

Parties have good reasons to avoid reaching back to politicians of prior generations. When they do, they bring forward not only the ideas of the past, but also the personalities and the quarrels of the past…

Yet the biggest risk to Democrats from a Hillary Clinton nomination is not that it would be generationally backward-looking — or that it would reopen embarrassing ethical disputes — but that it would short-circuit the necessary work of party renewal.

After eight years in the White House, a party requires a self-appraisal and a debate over its way forward. Bill Clinton offered Democrats just such a debate in 1992 with his “New Democrat” ideas. Barack Obama offered another in 2008 with his careful but unmistakable criticism of Clinton-era domestic policies and Hillary Clinton’s Iraq war vote. But if Hillary Clinton glides into the nomination in 2016 on the strength of money, name recognition, and a generalized feeling of “It’s her turn,” then Democrats will forgo this necessary renewal.