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.