I think it’s less about age than when they entered politics. If you look at the group of more progressive candidates that have risen since 2008 there’s a mix of late boomers. Gen xers and millenials. Even the group storming the gates now has that mix. Though they seem to be skewing younger and way more female.
And that rightward shift happened within the baby boom generation. It’s a subset. Came to head in the 80s. I think I’d have to look at the dates but it might be better to think in terms of political generations.
So as an example while you can pin point the early inklings of that rightward shift and the modern conservative movement to the dixiecrats, George Wallace’s presidential runs and Goldwater. You didn’t have any of that neccisarily building sustained national success until Nixon. The initial peak of it all came with Reagan’s election.
But if you look at the actual behind the scenes people on the right. The campaign people, the sub cabinet secretaries, the fundraisers, speech writers, diplomats, etc. And later often as elected officials. A freakishly large proportion of them had their first entry into politics, or first job in politics. As part of Nixon’s campaigns or during his presidential administrations. And these guys stayed largely in control of the GOP until pretty recently, when they basically started to die off. Huge amount of Bush II electric boogaloo’s campaign and administration were connected to these guys. A lot of them were involved with every administration from Nixon up till Obama. Including Carter and Clinton.
So it’s helpful to think of that set as “the Nixon generation” in American politics.
I’m willing to bet you can pin point an exact administration or series of campaigns where the bulk of these people started out, or followed on from.
It wasn’t McGovern, as he was the hopeful blinkered progressive that failed spectacularly. And most highly visible DNC members who started in and around his campaign seem to track at least center left. Even if they spent a long time hiding it. Doubt it would be Carter as his influence wasn’t lasting and he’s considered the last true liberal president between then and Obama. And there was a lag between increasing GOP far right success and DNC shifts. Both McGovern and Carter are considered first failures that started to drive the DNC away from their left wing. Maybe could be pegged as a response to Reagan. Or Bill Clinton’s early campaigns as his success in the face of a rightward shifting nation really seems to have had an effect that built out from those campaigns for Governor.
I’m willing to bet that’s a bigger predictor than actual age. Elizabeth Warren is almost 70. But she only entered government work in the 90’s as a regulator. And more political work in the 00’s, only running for office for the first time 5 years ago. Before that she had a pretty full career as a law professor (and she was a Republican). Sanders is 76, but started in politics all the way back in the 60’s. First seeking office in the late 60s. Well before the conservative shift (and also doesn’t seem to have ever really held down a job that wasnt and elected office).
They’re both certified boomers. But their involvement in politics brackets the period where it was exceedingly difficult to get votes on the left. Baring very limited places.
I really think we’re looking at a group of people, whatever age. Who entered politics in the very late seventies to very early 90’s. Probably in response to something specific that drew them in or gave them a job. Either because the political tenor of the era demanded it, or the people they were working with convinced them of a particular outlook.
ETA: Feinstein seems to have started in politics in 1969. And first got a major political seat in the late 70’s. As mayor of San Francisco. First after the assignation of Harvey Milk and Mayor George Mascone, then by election.