Ron DeSantis, the 44-year-old governor of Florida, has entered the presidential race, establishing himself as the most formidable Republican rival to Donald Trump.Mr. Trump, an inveterate liar who tried to overturn the last election, is alienating to a wide swath of voters, and many establishment Republicans have been happy to hunt out alternatives, particularly in Mr. DeSantis. After a rough midterm for Republicans that included the defeat of several Senate candidates endorsed by Mr. Trump, the former president appeared vulnerable.But since then, it has grown clear that counting him out as the likely Republican presidential nominee is foolhardy. Several factors — among them, the intense support he draws from a sizable chunk of the Republican base and his singular talent for commanding media attention — help explain why Mr. Trump holds a commanding position in the primary. History offers at least one parallel for why it will be so difficult for Mr. DeSantis and other G.O.P. contenders, like Nikki Haley, 51, the Trump administration’s ambassador to the United Nations, and Senator Tim Scott, 57, Ms. Haley’s fellow South Carolinian, to take him down.There was, more than a half century ago, another de facto leader of the Republican Party who reeked of failure. Pundits mocked and dismissed him as a has-been. Rivals across the ideological spectrum no longer feared him and cheered on his slide into irrelevancy.By the end of 1962, few believed there was a future for Richard Nixon, the former vice president. In 1960, he lost one of the closest-ever presidential races to John F. Kennedy, and members of the liberal Republican establishment, including Dwight Eisenhower, were glad to see him fall.After losing to Kennedy, Nixon tried to regroup, entering the 1962 California governor’s race against the well-liked Democratic incumbent, Pat Brown. Nixon, who had served as a representative and senator from the state, was initially expected to triumph and use the governorship as a steppingstone to the presidency. Instead, Brown swatted Nixon away after the former vice president had to endure a bruising primary battle against a Republican who was popular with the sort of movement conservatives who would, in the coming years, seize control of the party.On the morning after his loss to Brown, Nixon famously told the assembled press at the Beverly Hilton Hotel they wouldn’t have him to “kick around anymore.” That November, the journalist Howard K. Smith titled a television segment “The Political Obituary of Richard M. Nixon.”In the wake of these humiliations, Nixon’s tenuous comeback hinged on persuading both Republican voters, who could find more attractive warriors for their cause, and influential party and media elites that he in fact wasn’t completely finished. In 1964, Nixon flirted with running for president but backed away. (Mr. Trump, of course, did not feel chastened for supporting weak and beatable candidates in the midterms last year, and instead waited roughly a week to announce another presidential run.)Nixon decided to support Barry Goldwater, the far-right Arizona senator who lost in a landslide to Lyndon Johnson, the Democratic president. Nixon’s attachment to Goldwater won him some plaudits with the base of the party — he had been one of the few prominent Republicans to stick with the senator — but didn’t help alter the perception that he was a serial loser. To complete his rehabilitation, in the 1966 midterms, he strategically stumped for anti-Johnson Republicans who were poised to ride the white backlash to the Great Society and civil rights programs.By 1968, Nixon had established himself as a foreign policy maven, having undertaken many world tours in the 1960s, and cast himself as an arch, erudite critic of the Johnson administration.His period of vulnerability was briefer, but Mr. Trump today, like mid-’60s Nixon, has reasserted himself as a party kingpin. Now he, too, is contending with a popular governor from a large swing state.In the 1968 G.O.P. primary, Nixon actually had to outflank three prominent Republican governors — George Romney of Michigan, Nelson Rockefeller of New York and Ronald Reagan of California — who could offer, in the immediate term at least, more allure.Reagan, who had defeated the formidable California Governor Brown in 1966, was actually older than Nixon but had the swagger and ease of a much younger man, marrying the sort of sunny optimism Nixon could never muster with the raw appeal to a growing reactionary vote that Nixon craved.Just as Mr. DeSantis, with his wars on critical race theory, “woke” Disney and Covid restrictions, is trying to outmaneuver Mr. Trump on the cultural terrain that’s always been so vital in Republican primaries, Reagan outshone Nixon with his open disdain for Johnson’s landmark civil rights agenda, the burgeoning antiwar movement and the emerging hippie counterculture. He railed against the “small minority of beatniks, radicals, and filthy-speech advocates” upending California and successfully demoralized Brown, who remarked, shellshocked, after Reagan’s triumph that “whether we like it or not, the people want separation of the races.”Nixon rebuffed Reagan and the others in one of the last primaries where delegates and party insiders, rather than the will of voters, played a significant role in determining the nomination.Here the present diverges from history. Nixon was far more introspective, methodical and policy-minded than Trump. He was, by 1968, a significantly stronger general election candidate, winning the most votes — Trump has twice lost the popular vote — despite the segregationist George Wallace’s third-party bid, which ate into Nixon’s support.But just as a divided primary field worked to Nixon’s advantage, so it may for Mr. Trump, especially if several other candidates become viable. In such a scenario, Mr. Trump may need only pluralities in pivotal early states to take the nomination. His core fan base might be enough. Though Mr. Trump’s 2016 campaign was often shambolic, it managed a finely tuned nativist, anti-free trade and anti-globalization message that cut through the noise of a chaotic primary season. In Nixonian fashion, Mr. Trump tapped into his party’s reactionaries and delighted the grass roots.The question is whether Mr. Trump can do it again. One of Nixon’s great political strengths was to assume, even at the height of his powers, the position of the aggrieved — to convince a palpable mass of voters that they, and he, were the outsiders. Genuinely self-made, this posture came naturally to Nixon. Mr. Trump, though the son of a millionaire real estate developer, has nevertheless effectively adopted it throughout his political career, once boasting of his love for the “poorly educated.”Mr. DeSantis enters the fray hoping that Mr. Trump’s many flaws, continuing legal troubles and political baggage ultimately render him weaker than he appears today. But looking at the historical parallel, even Reagan, a once-in-a-generation political talent, could not dislodge Nixon. As Mr. DeSantis’s Twitter-launch debacle suggests, he will need to quickly, and considerably, improve his standing. Perhaps then, with the help of a Trump implosion, can he hold out hope for 2024 — or even, as Reagan’s example suggests, a future presidential run.If 1968 is any guide, Mr. Trump will be tough to beat. In a crowded field, among a hungry younger generation of contenders like Mr. DeSantis, he will have to manufacture anew this kind of populism. He might just do it.Ross Barkan is an author and a contributing writer to The New York Times Magazine.The Times is committed to publishing a diversity of letters to the editor. We’d like to hear what you think about this or any of our articles. Here are some tips. And here’s our email: letters@nytimes.com.Follow The New York Times Opinion section on Facebook, Twitter (@NYTopinion) and Instagram. More