People would always ask him: “What do you want to do as a career?” Robinson said.

“What’s wrong with graduate school as a career?!” Lehrer would respond. He spent some 15 years working on and off on his dissertation, until he finally gave it up in 1965.

The space for one of the animating forces in Lehrer’s music, his liberal politics, was shrinking too. Lehrer was a hero of the anti-nuclear, civil rights left; he occupied the bleeding edge of the elite liberalism of the day. “I Wanna Go Back to Dixie” minces no words in its scorn for the industry of American nostalgia, and particularly for the American South: “I wanna talk with Southern gentlemen / And put my white sheet on again / I ain't seen one good lynchin' in years ... The land of the boll weevil / Where the laws are medieval / Is callin' me to come and nevermore roam.”

But his left was the square, suit-wearing, high-culture left. His circle at Harvard included Arthur Schlesinger Jr., the renowned historian, JFK biographer, and then-nominal chairman of the Cambridge chapter of Americans for Democratic Action. His political hero was Adlai Stevenson, the Democratic Party’s presidential candidate in 1952 and 1956, the man whom Richard Nixon damagingly dismissed as an “egghead.”

Stevenson’s losing battle marked the end of a political tradition, and also the beginning of the end of a kind of Ivy League liberal intellectualism's place atop the Democratic Party. What was coming was the New Left and the counterculture, something whose aesthetics Lehrer couldn’t stand, even if their politics weren't necessarily at odds.

“It takes a certain amount of courage to get up in a coffeehouse or a college auditorium and come out in favor of the things that everybody else in the audience is against, like peace and justice and brotherhood and so on,” he deadpans in his introduction to the whiny “Folk Song Army” on That Was the Year That Was. “We are the folk song army / Everyone of us cares / We all hate poverty, war, and injustice / Unlike the rest of you squares.”

The New Left agreed with Lehrer on Vietnam. His last public performance, in fact, was on a fundraising tour for George McGovern in 1972. But the singer — who saw himself as “a liberal, one of the last” — felt less at home in the new Democratic Party. In the end, Stevenson’s party, and Lehrer’s, lost — and with it, at least to Lehrer's mind, a prevailing sense of humor. “Things I once thought were funny are scary now," he told People magazine in 1982. "I often feel like a resident of Pompeii who has been asked for some humorous comments on lava.”

''The liberal consensus, which was the audience for this in my day, has splintered and fragmented in such a way that it's hard to find an issue that would be comparable to, say, lynching,” he also told the New York Times in Purdum’s 2000 article, which was part of his last round of interviews to promote an anthology of his work. ''Everybody knows that lynching is bad. But affirmative action vs. quotas, feminism vs. pornography, Israel vs. the Arabs? I don't know which side I'm on anymore. And you can't write a funny song that uses, 'On the other hand.'''

By the late 1960s, Lehrer had no clear direction. His musical career was over, as far as he was concerned. His academic career had stalled. He didn’t like the cold. So he found a new home, perhaps surprisingly, at an institution that embodied the radical spirit of the 1970s, and rejected the conventional liberal consensus he was mourning. The University of California at Santa Cruz had embarked on an experiment in multidisciplinary education that appealed to Lehrer. The motto, recalled Dr. Tony Tromba, a UCSC professor who was on the hiring committee that brought Lehrer to campus in 1971, was “Distilling truth in the company of friends.”

Contrary to many colleges in the UC system, Santa Cruz eschewed the word “department,” favoring the idea of its professors teaching on “boards of studies.” Some of Lehrer’s best songs are about math and science — “New Math,” “The Elements,” and “Lobachevsky” are as funny, and educational, now as they were 50 years ago, and heralded the rise of cultural touchstones like Sesame Street. (In the 1970s, Lehrer wrote briefly for the educational show The Electric Company.) Lehrer was hired to teach a musical theater class in the history department, though he would eventually teach math at the university as well, spending winter semesters at Santa Cruz, yet continuing to be in Cambridge in the spring.

“He created an enormously positive experience for students,” Tromba said. “I don't know of a single person who didn't love him."

Lehrer would teach and loosely direct his favorite musicals, one from each decade up to the '70s, every two weeks, which the students would then perform in a campus lounge. Throughout the incredibly laid-back and casual course (Lehrer would admit in a 1980 BBC radio interview he was surprised the university even gave credit for it), he’d also expose students to his vast knowledge of musical theater history, lyricism, and composition.

“He would tell us the historical relevance of the musical we were doing," said Kim Leatherman, who was in Lehrer’s class in 1988. "We did The Pajama Game, so he would tell us the relevance of the 7 1/2 cent wages and [what] the workers were saying. It was like a history lesson as well as a musical theater class.”

Perhaps revealing Lehrer’s proclivity for those, like him, who don’t have to try too hard, Leatherman auditioned for his class on a complete whim and was accepted at the expense of friends who had been dying to get in. And in addition to the lasting fondness his students expressed for their onetime teacher, they also all mentioned in interviews one of the characteristics that continues to make Lehrer such an enigmatic figure among his fans.

“He was one of the most private people I’ve ever met,” said another former student, Jamey Harvey, adding that it was an unspoken rule in Lehrer’s class that you didn’t mention his career as a performer. “It would have felt very intrusive to ask, between the warnings we got from our friends and the body language you got when you asked him about it. My sense was he thought it was embarrassing.”

His personal life, too, has been off limits, even to friends. Asked once by Jeff Morris if he’d been married or had children, he replied: “Not guilty on both counts.”

And rather than accept any admiration those around him might have had for his past successes, Lehrer was content to be proud of the work of his students, and of his colleagues who did theater. “He was a fan of us, the theater people there, which is just remarkably generous and humble of him,” recalled Danny Scheie, a drama professor at Santa Cruz who first met Lehrer in the early '90s in Santa Cruz’s musical theater crowd.

Yet despite his retreat into a comfortable, bicoastal existence as an instructor on two college campuses, Lehrer has maintained an uncanny popularity, especially for a performer whose career totaled only a few years.

Around the time Lehrer was hired at UCSC, Mackintosh approached him with the idea to produce Tom Foolery. The show opened in London in 1980 and was by and large a success, eventually touring in Canada and produced for far-reaching audiences in South Africa and China. The show, slated for performances in Michigan and Washington later this year, continues to reward Lehrer with royalties. To date, he has sold more than two million records.

Between 22 years on The Simpsons and co-creating This Is Spinal Tap and A Mighty Wind and having his own radio show for 30 years, Harry Shearer knows a lot about the nexus of pop music and comedy, and cites Lehrer as one of his “principal inspirations," particularly in the way he wrote and performed original music — and expertly — rather than just adding parody lyrics to known songs.

“Had he not withdrawn from the field," said Shearer, "I suspect he'd still be at the top of his class."