Editor's Note: (Julian Zelizer is a professor of history and public affairs at Princeton University and a New America fellow. He is the author of "Jimmy Carter" and "The Fierce Urgency of Now: Lyndon Johnson, Congress, and the Battle for the Great Society." The opinions expressed in this commentary are his.)
(CNN) The big news coming out of South Carolina was obviously Donald Trump's decisive 10-point victory. No longer the maverick, no longer the insurgent, no longer the question mark -- Trump is now the clear front-runner in the race for the Republican nomination.
Sen. Ted Cruz was unable to turn his advantage with the evangelical right into electoral success. With his formidable ground operation and fund-raising apparatus, it would be a huge mistake to write him off. Yet now he is clearly running to catch up with Trump, rather than alongside him.
But South Carolina was also important because it began to clarify who the "anti-Truz" candidate would be. The results in the Palmetto State were significant. Marco Rubio, who has been picking up steam, remains in pretty good position going into Super Tuesday, though his delegate count is low.
Coming in second, Rubio was able to rally the support of many key figures in South Carolina, including the tea party darling Gov. Nikki Haley. Jeb Bush's announcement that he was suspending his campaign gave Rubio another important boost, assuming that much of Bush's support from major figures in the party will drift his way.
At this point in the campaign, what are Rubio's strengths? For many Republicans, the 45-year-old senator from Florida remains the candidate who sends a desirable message about their party. He is young, he has a rags-to-riches story, he is part of the culturally diverse nation that waves of immigration have created in America. His rhetoric is optimistic and it is often bold. During many debates he has shown a strong command of the substance of public policy.
With so many people believing that the Republican Party has drifted drastically to the right -- with abrasive, nativistic and hostile rhetoric shaping many of the party's leaders -- a vote for Rubio would send a message that the image of an extremist party is not accurate. Republicans are more than a party for older, angry white males, a Rubio victory would demonstrate.
At the same time, Rubio has been able to pull off a Reaganesque trick. He can make all of these kinds of claims with a policy record that is staunchly conservative.
His success would not be a victory for moderation, but rather a vindication for the right. Republicans can vote very conservative with Rubio while still appearing interested in the center.
Rubio, many forget, was one of the first major candidates to come out of the tea party movement. Although he unsuccessfully attempted to push through Congress an expansive immigration bill, the rest of his record has been far to the right. And during the caucuses and primaries he has dug in even further, including on immigration, where he has backed away from any sense of moderation. As Frank Bruni argued in The New York Times, if Rubio does appeal to moderate Republicans, "that's not a function of his record or his positions on a range of issues." Like Ronald Reagan in 1980, Rubio has the capacity to sell conservatism with a smile.
Now Rubio will be in a strong position to start rounding up all the party endorsements that social scientists have said are so important to the selection of the candidate. The endorsements, combined with campaign contributions that will be redirected from Bush to him, will offer Rubio the power of the party apparatus to wield against Trump.
Assuming that John Kasich doesn't have much success against Rubio outside of a few states like Ohio and Michigan, very soon we can see the so-called party establishment coalesce around the Floridian in a full-scale effort to end Trump's surging candidacy. Until now the party establishment has been deeply divided, and thus unable to put all of its heart and soul behind any of the candidates.
While Rubio has not yet won a state, the big competition is still coming. Since Trump's candidacy is so unusual and so unpredictable, its underlying durability remains uncertain.
Rubio's path to victory is to do well in some of the upcoming Southern contests on Super Tuesday where voters are not as tolerant of Trump as in South Carolina, while besting Ted Cruz in Northeastern primaries like New York and Pennsylvania, where voters want someone who at least seems like the most moderate and reasonable candidate in the bunch.
Not unlike Hillary Clinton, one of his selling points will be that he is the most "electable" candidate from his party, an issue which came up as a strong factor for those who supported him in South Carolina. One of the biggest questions will be whether and when John Kasich drops out of this race, thereby creating another pocket of electoral support that Rubio can pick up from those voters who don't believe that Trump could win a general election.
But will this all be enough? If there is a lesson from South Carolina, the one-time "firewall" that Lee Atwater created to make sure the GOP establishment could defeat any insurgents, it is that the party is not as strong as people once thought.
Trump has demonstrated that the 2016 campaign -- with its sources of independent financing and the multitude of media opportunities for candidates to spread their message directly to voters through social media and 24-hour news -- has opened up the process in ways that experts never imagined.
The intense anger and frustration among Americans about the economy and about Washington have created an electorate that finds Trump's style of politics incredibly appealing.
And like it or not, Trump is proving to be a shrewd politician. Rubio has a tough fight on his hands. Trump has been masterful in understanding how to keep the media's attention, and his eclectic mix of anti-establishment rhetoric, nativism, attack politics and smorgasbord policies is starting to build the kind of winning coalition that produces a nomination.
Trump's victory suggests that Republican voters are willing to be more flexible and strategic than many expected if they see a candidate who can take the White House (including supporting someone who spoke favorably of the Obamacare mandate, although he has backed away from that).
Finally, there are a number of historical examples -- like Barry Goldwater in 1964 or George McGovern in 1972 or even Jimmy Carter in 1976 -- in which "electability" didn't win out in the decision-making process of many voters who were upset with the status quo.
Right now is Rubio's moment, his opportunity to take the front-runner status away from Trump and become the kind of new Republican force that many believed he could be early in the campaign.
The South Carolina second-place showing was as meaningful to him as the victory was to Trump. But to take Trump down, especially as The Donald turns all of his rather devastating firepower toward him, Rubio will need to engage in a much sharper style of counterattack politics and to loosen up a bit in the campaign to shed some of the robotic image that raises questions about how much of what he says is scripted.
But anyone who continues to dismiss Rubio is making a mistake. He has the potential to win this nomination, and there are good reasons that he remains the Republican whom the Hillary Clinton camp is most worried about facing in a general election.
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