Twenty years ago, a chubby and nearly unibrowed high school senior in South Bend, Indiana wrote an essay about his political idol, the then-57-year old Vermont Congressman who was unafraid to call himself a socialist. Tonight, after effectively tying the Iowa caucuses, that young man will face off against his former idol: Pete Buttigieg and Bernie Sanders will go head to head in the final debate before the New Hampshire primaries next week.

In the essay, which was written in 2000, Buttigieg earnestly applauded politicians who “eschew political and personal comfort and convenience because they believe they can make a difference.” He cited Sanders as “one outstanding and inspiring example of such integrity” and praised him for his willingness to “stand against the current of opportunism, moral compromise, and partisanship which runs rampant on the American political scene.”

His essay, which won the JFK Profiles in Courage contest, ended with a line that now seems like a premonition:

Above all, I commend Bernie Sanders for giving me an answer to those who say American young people see politics as a cesspool of corruption, beyond redemption. I have heard that no sensible young person today would want to give his or her life to public service. I can personally assure you this is untrue.

Now, of course, Buttigieg may be wishing he’d picked a different subject for his essay—and Sanders may be wishing that Buttigieg had found him a little less inspirational.

The Iowa Caucuses, the results of which remain muddled, appear to have resulted in a virtual tie between the two candidates. Buttigieg has used that momentum to jump in the polls in New Hampshire; he’s now just a point behind Sanders, well within the margin of error.

And high school kid who once heralded Sanders for his convictions and principles is now openly criticizing him as an uncompromising ideologue. In that two-decades-old essay, Buttigieg described Sanders as a “a powerful force for conciliation and bi-partisanship on Capitol Hill,” and praised him for his “reputation as a peacemaker.” Now, Buttigieg accuses Sanders of embracing what he calls a “my way or the highway” approach.

“I hear Senator Sanders calling for a kind of politics that says ‘you’ve got to go all the way here and nothing else counts,’” Buttigieg said in Iowa last week. He added that his two main opponents, Sanders and former Vice President Joe Biden, were stuck litigating the “arguments of the past.”

When asked about the essay in his CNN town hall Thursday night, Buttigieg explained that he had commended Sanders’s bravery, not necessarily his ideology. “What I really admired about Senator Sanders —and still do — is his consistency and willingness to say exactly what he believes,” Buttigieg said. “It doesn’t mean I agree with him. I didn’t agree with him on everything then and don’t agree with him on everything now. But I do believe that wherever we fall on some pundit’s ideological spectrum, we have a responsibility to talk about what we believe in and to make the case for what we think it’s right, when it’s popular and when it’s not.”

Meanwhile, the Vermont Senator is punching back against his former acolyte. “I’m reading some headlines from newspapers about Pete Buttigieg,” he said at an event in Manchester Friday morning, enunciating Buttigieg’s name slowly as if he hadn’t quite gotten used to saying it yet.

“Pete Buttigieg has most exclusive billionaire donors of any Democrats, that was from Forbes,” Sanders said. “The Hill: Pete Buttigieg tops billionaire donor list. Fortune: Pete Buttigieg takes lead as big business candidate in 2020 field. Washington Post: Pete Buttigieg lures even closer look from Wall Street donors following strong Iowa caucus performance. Forbes magazine: here are the billionaires backing Pete Buttigieg’s presidential campaign.”

Most of all, the essay reads as a reminder of the gaping, forty-year age difference between the two Democratic frontrunners: Buttigieg, 38, is young enough to have looked up to Sanders when he was a kid, while Sanders, 78, is old enough to be competing against someone nearly young enough to be his grandchild. And in there, the essay contains the seed of both frontrunners’ arguments against each other: Buttigieg arrived too soon, and Sanders stuck around for too long.

Correction, Feb 8. The original version of this story misstated the age difference between Bernie Sanders and Pete Buttigieg. It is 40 years, not 50 years.

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Write to Charlotte Alter at charlotte.alter@time.com.