Marco Rubio is officially in the race for the Republican nomination, but as an outsider. Photograph by Wilfredo Lee/AP

Whatever happened to Marco Rubio? In February, 2013, his picture appeared on the cover of Time magazine, accompanied by the headline “The Republican Savior.” At the time, many political analysts—Bill Clinton reportedly among them—viewed the Florida senator as a big threat to the Democrats in 2016. Now, following his announcement on Monday in Miami, he’s officially in the race for the Republican nomination, but as a rank outsider. According to the Real Clear Politics polling average, just 7.5 per cent of likely Republican voters consider him their first-choice candidate. That puts him in seventh place, behind Jeb Bush, Scott Walker, Ted Cruz, Rand Paul, Ben Carson, and Mike Huckabee.

Of course, it’s early in the process. Having gone all in, Rubio might get a boost, just as Cruz, the junior senator from Texas, has since he announced his candidacy last month. Right now, though, it’s hard to see how he could challenge the front-runners. Although Rubio was elected to the Senate in 2010 as part of the Tea Party wave, and although he still espouses extreme views on issues like climate change (he’s a skeptic) and same-sex marriage (he opposes it), many people in the conservative movement don’t view him as a true believer. In any case, the right-wing end of the Republican field is very crowded. Rubio’s best hope is probably to position himself as a center-right candidate and hope for a slipup on the part of Jeb Bush, his fellow Floridian.

The proximate cause of Rubio’s current problems is well known: his role in co-sponsoring a bipartisan immigration-reform bill that would have established a lengthy pathway to citizenship for law-abiding undocumented immigrants. With the support of Rubio and thirteen other Republicans, the Senate passed the bill in June, 2013. After the bill generated a backlash among conservative and anti-immigration groups and died in the House of Representatives, Rubio backtracked, disavowing the legislation and saying that it wasn’t realistic. But the damage to his reputation on the right had been done. And so, as the race to 2016 began to shape up, Rubio found himself outflanked by other conservative hopefuls, such as Cruz and Walker.

In the past year or so, Rubio has been trying to regain the trust of his party’s hard-liners, saying that nobody has an automatic right to immigrate to the United States and stressing that improving border security should be the first priority. He’s had some success in this enterprise. “I think that Sen. Rubio has done something that most politicians don’t do,” Jenny Beth Martin, the president and co-founder of the Tea Party Patriots group, told Politico. “He evaluated what went wrong ... [and] is working to make sure he doesn’t make the same mistakes again. I think that neutralizes his mistakes.”

But what use is a Marco Rubio who panders to the right on his defining issue? The Republican Party is chockablock with supine politicians of this sort, and that helps to explain why it has lost the popular vote in five of the last six Presidential elections. The thing that made Rubio an exciting figure a few years ago, the reason he landed on the front of Time magazine, was that he seemed to combine youth, a compelling personal story, and conservative views with a willingness to reach out to parts of the electorate that the G.O.P. had neglected, particularly, but not exclusively, Hispanics. Immigration reform was supposed to be the test case for whether the Republican Party could adopt a more pragmatic and inclusive approach, and when it sunk, it took Rubio down with it.

The bigger story is that this Republican golden boy fell victim to what I refer to as the three-strikes theory of politics. If you look around, you will find that it generally takes not just one or two but three defeats for an unpopular political party to reform itself and abandon the things that made it unpopular. Because of the influence of established politicians, vested interests, and ideology, all democratic parties tend to resist change. Two strikes aren’t enough to overcome this inertia. Only after a third successive beating at the hands of voters can reformers overcome the ideologues and seize control of the party.

Of course, it’s only a theory, and it has its exceptions. But look at what happened to the Democratic Party in the nineteen-eighties. After losing to the Republicans for a third successive time in 1988, Bill Clinton and his business-friendly “New Democrats” gradually gained the upper hand and won the 1992 election. Something similar happened in the United Kingdom, when the Labour Party, after defeats in 1981, 1984, and 1987, jettisoned much of its ideological baggage: its commitments to public ownership, unilateral disarmament, and compulsory trade-union membership. The more recent experience in France, which saw the Socialist Party lose Presidential elections in 1995, 2002, and 2007, isn’t quite as stark, perhaps, in that the current President, François Hollande, could hardly be described as a great departure from previous Socialist leaders. But even Hollande, in the run-up to the 2012 Presidential election, advocated for some policies that had previously been considered off limits, such as raising contributions to the retirement system and making it easier for businesses to hire and fire workers.

Where are the Republican reformers? Despite talk about making the party more electable, the evidence suggests that the G.O.P. ultras, even if they don’t hold many very senior posts in the party, retain an effective veto over any efforts to modernize. With Rubio now parroting the immigration line laid down by Rush Limbaugh, Sean Hannity, Glenn Beck, et al., the task of taming the right wing has passed to Bush, who, to his credit, has not yet backed down from his support for comprehensive immigration reform, including a path to citizenship for the undocumented.

As I’ve mentioned before, Bush is hardly a moderate. During his eight years as governor of Florida, he pursued a stridently conservative agenda on spending, taxes, labor laws, and many other issues. Still, compared with the likes of Cruz, Walker, and Carson, he’s practically a Rockefeller Republican. But if you look at the surveys of Republican voters collected on Real Clear Politics that I cited earlier, you will find that Bush is stuck at well under twenty per cent. If you then add together the vote shares of Walker, Cruz, Paul, Carson, and Huckabee, all avowedly conservative candidates, you get a total of 53.1 per cent. Add in Rick Perry and Rick Santorum, and the conservative tally is even higher.

Based on this evidence, the G.O.P. doesn’t look like a party that is ready to embrace change. And that’s why Rubio already looks like an also-ran. Falling afoul of the three-strikes rule, he peaked one election cycle too early.