When I met him in 1994, Martin McGuinness was decisively stepping away from those decades of violence. It was the day the I.R.A. finally declared a cease-fire — a hurdle overcome in the political negotiations that led ultimately to the Good Friday agreement.

Mr. McGuinness’s role in the I.R.A. is still shrouded in secrecy; I was there to interview him, briefly, for NPR. We spoke in a grubby room full of discarded boxes and old office furniture. I asked him the obvious questions, but I remember two things: listening to him and thinking, this guy is only three months older than I am and look at the things he has done; Mr. McGuinness, unguarded and unsure, asking, how do you think we’re doing?

I thought he meant, how did I think Sinn Fein was handling the media attention it was getting. The Irish Republican leaders were a secretive crew, and they now had to deal with hundreds of journalists from all over the world. I also got the sense he meant himself personally, “How am I doing?” He was taking the first step from being a revolutionary — or terrorist, you decide which — toward becoming a legitimate politician, a disorienting change for a middle-aged man.

It was a very human moment. He had hazarded his life on the violent overthrow of the existing order, and now after 20 years was — by his actions, not his words — acknowledging that it had been the wrong tactic. That day at the end of August 1994 I felt the need — ’68er to ’68er — to assure him he was doing just fine. The words were awkward. I wanted to go deeper. A Sinn Fein press officer came for him, and the interview was over.

Today, Mr. McGuinness is deputy first minister of Northern Ireland, and completely at home in the impure world of mainstream party politics.

I have interviewed other men and women my age who were part of revolutionary movements and imprisoned and tortured for it. While we spoke of revolution in America, swigging beer and withholding our votes, these people had walked it like we talked it.

I wonder if young supporters of Bernie Sanders and their peers have the patience for the hard work of change. I don’t think it was revolutionary, but it was incredibly radical for a Brooklyn Jew to move to Vermont in that extraordinary year of 1968. Vermont was a Republican state. It took more than a decade for Mr. Sanders to figure out how to win an election there.

I hope that the reported one-third of voters ages 18 to 29 who say they will vote for a third-party candidate are asking themselves if they know the difference in price between T-shirt revolution and the real thing.