The recent death of former congressman and third-party presidential candidate John Anderson is a peculiar milestone in U.S. political history, something like the final Lincoln Town Car rolling off the assembly line or the passing of the last Civil War veteran.

Anderson was a famous example of a now-extinct breed of politician, the liberal Republican, even if there was little that was particularly noteworthy about the man himself.

Of course, there was his 1980 presidential campaign. Anderson caused a stir that summer, polling as high as 26 percent in a three-way race against President Jimmy Carter and Ronald Reagan. But third-party presidential hopefuls always see their support erode as November approaches, and Anderson was no exception. He ultimately finished with less than 7 percent of the vote.

For context, that's much less than George Wallace or Ross Perot won in their respective independent runs, and closer to that year's Libertarian Party ticket of Ed Clark and David Koch (yep, that David Koch) than to either major-party candidate. Anderson's signature pledge to increase the gas tax by 50 cents ($1.49 per gallon in today's dollars) — during a historic fuel shortage! — appealed to college students and a certain kind of liberal intellectual, but few others.

Anderson actually lost two races in 1980: his independent run in the fall, and an earlier effort to capture the Republican nomination from conservative activists led by Reagan. His failure to win greater acceptance, either from Republicans or the public at large, was a sign of the conservative movement gaining steam in the 1970s. That's when the right began casting aside its pragmatists for true believers.

It hasn't looked back since.

After his strong primary challenge to then-President Gerald Ford in 1976, Reagan was the presumed front-runner for 1980. If someone was going to stop him, Anderson was far down the list of possibilities, behind such people as Ford, George H.W. Bush and Howard Baker.

Still, Anderson embodied everything that the former California governor and his followers were rebelling against. He was part of an endangered species known as the Rockefeller Republicans, moderate where the Reaganites were conservative, staid where they were revolutionary and Eastern where they were Western.

Indeed, after so many years of conservative dominance over the GOP, it is almost unthinkable that a man as ideologically distinct as Anderson could have won any office under the Republican banner. A 10-term fiscal conservative, he nonetheless supported abortion rights and gun control. Initially a reliable GOP foot soldier, he began drifting from conservative orthodoxy in 1968 while stumping for the anti-discrimination measures in the Fair Housing Act.

The political climate in the Republican Party in the late 1960s was such that even as Anderson adopted more liberal positions, his stature continued to grow. In 1969, he was chosen as chair of the House Republican Conference, the third-ranking House leadership position in the party. During the Watergate scandal, he emerged as one of President Richard Nixon's most prominent critics in the House, and he was later the only Republican candidate to back the SALT II arms reduction talks with the Soviet Union in 1980.

Those are the kinds of apostasies that would buy you a primary opponent today, and as politics changed during the 1970s, even Anderson's national standing couldn't ward off a series of increasingly perilous challenges from the right. After barely fending off conservative pastor Don Lyon in 1978, he decided to make a stab at the presidency rather than seek another term. "I don't think I'm being paranoid when I say that I'm the test case for this whole effort to purge the Republican Party of any progressive element," he complained to Washington Post reporter David Broder during the primary campaign. "If they defeat the chairman of the House Republican Conference, they can put the fear of God into a lot of other Republicans."

Setting aside the retrospective dissonance of a Republican making favorable use of the term "progressive," Anderson was absolutely correct in his analysis.

Until that time, there had been a roughly identical distribution of ideological warriors in both major parties. But in the years leading up to the fateful 1980 presidential election, the percentage of hyperpartisans and ideologues in the House Republican caucus skyrocketed. Lots of factors contributed to that change: the party's growth in the conservative South, influential conservative media outlets like National Review, the influx of conservative evangelicals into politics and the rise of the religious right. As a result, the hyperpartisanship of the GOP has kept increasing for nearly 40 years, with no end in sight.

More than any conservative policy victories achieved during the Reagan administration (whose budgets tended more toward pragmatism than orthodoxy), this was the most meaningful result of what has come to be called "the Reagan revolution." Party grandees like Bush and Baker were powerless to stop it — conservatives had far more robust grass-roots infrastructure.

Notice was served down the chain as well: In 1974, 240 House members fit in the ideological space between the most conservative Democrat and the most liberal Republican. Today, that number is zero.

As the center disintegrated, party-switching came into vogue. Yankee Republicans like New York City Mayor John Lindsay (along with his young assistant, the Californian Leon Panetta) became Democrats, while archconservative Southerners like Jesse Helms, Strom Thurmond and John Connally moved in the opposite direction.

Adherence to Republican doctrine increasingly meant being skeptical of civil rights activism and social programs, disdainful of the counterculture and fiercely anti-communist. Anderson was suddenly shunted to the left-most seat in the pew: He supported the Equal Rights Amendment when Phyllis Schlafly was becoming the most famous conservative activist in America as its fierce opponent; he favored detente when a growing faction of neoconservatives — most of them freshly defected former Democrats — were counseling ever-greater confrontation with the Soviets.

By refusing to change with the times, Anderson won the admiration of the high-minded commentariat. In 1980, the New Republic backed Anderson as an acceptable alternative for liberal voters disgusted with Carter. A somewhat bemused Atlantic profile extolled his abilities, experience and track record, even as it lamented his slim chances of breaking through. Celebrities like Paul Newman and Norman Lear lent their support, and Jacqueline Kennedy Onassis and Arthur Schlesinger gave him Camelot's vote.

But he also found himself a man without a party. Formerly a mainstream leader of a party dominated by moderates, Anderson wound down his career advocating for a variety of quixotic political causes, from ambitious electoral reforms to the presidential candidacy of Ralph Nader. Although he endorsed a few Democrats over the years, including Barack Obama in 2008, he never joined that party.

Since 1980, the Republicans have been America's dominant political force. By the end of Donald Trump's first term, they will have controlled the White House for 24 of the last 40 years. They have controlled the House of Representatives for 18 of the last 22.

Power has not brought peace, however. Since Reagan overthrew the Rockefeller Republicans, new insurgents have picked up the banner of permanent revolution, from Pat Buchanan to Newt Gingrich to Ted Cruz to Donald Trump. Congressional leaders are toppled by palace coups more often than they retire willingly. And as each new purist rose to displace the prior generation's, the party's philosophy has moved steadily rightward.

John Anderson, and the millions who voted for him in 1980, would find little reason to return to the party he left.

Kevin Mahnken is a writer living in New York. This article first appeared in the Washington Post.