Moreover, governors are often the strongest candidates for the White House — six of the Republican candidates have held that job — but the last two midterm elections left only 18 Democrats in the nation’s statehouses (17 after Kentucky’s recent election), and few, other than the governor of California, Jerry Brown — older than all the other candidates — who could point to success in an executive role.

But there’s more to it than that. Politically active Democrats of this post-boomer generation (my own) should admit that our experience is a bit out of step with the tone and demands of current politics. Unlike baby boomers, we weren’t brought up on the campus activism of the late 1960s, and we didn’t describe ourselves as “searching for more immediate, ecstatic, and penetrating modes of living,” as Mrs. Clinton did in her Wellesley commencement speech in 1969. The formative experiences of older Generation Xers were in the quiescent Reagan years, when civic life offered neither the sense of affirmative mission of the civil rights era nor the intense protests and passions of the late 1960s.

As a few members of this generation found their way into politics and government, it was usually not through the voluntarism and culture of service that emerged in the late 1990s, exemplified by Teach for America, nor the intense progressive — and unapologetically partisan — organizing of the 2000s, in vehicles like MoveOn.org or campaigns like the Vermont governor Howard Dean’s 2004 presidential bid.

If we got involved in politics and government at all, it was as a vocation. (I was a congressional staffer in the 1990s.) From dreary experience, even liberals learned to be wary of grand progressive ambitions, like President Bill Clinton’s health reform proposal, lest they invite backlash from an electorate we had been taught to identify as “Reagan Democrats”: culturally conservative, wary of change, but still expecting support from government. Our generation — the triangulation generation — devised anti-crime policies and welfare reform, got nervous at the mere mention of same-sex marriage, was taught that government should work through market mechanisms, rather than act as a countervailing force, and learned to govern through inoffensive gestures like tax credits.