Rubio wins in Puerto Rico. Is that a big deal?

The Florida senator has been neglected at the primary polls, despite major GOP figures' support. Can an island of 3.5 million, who can't actually vote in November, help him change course?

GOP presidential hopeful Sen. Marco Rubio celebrated his primary win in Puerto Rico, an unincorporated territory home to 3.5 million Americans who cannot vote in the general election, as a stepping-stone to success for the on-again, off-again favorite who has won the majority of delegates in just two out of twenty primaries so far.

Puerto Rico "is evidence I can take conservatism to people who don't normally vote Republican," the Florida senator told the Associated Press, emphasizing that he campaigned "as a conservative" and still won more than 70 percent in the open primary. 

Puerto Ricans cannot vote in the general election, but send 23 delegates to the Republican convention in July. Senator Rubio has also won Minnesota's Republican primary, earning 17 delegates.

Mr. Rubio has racked up an impressive series of endorsements, including South Carolina Gov. Nikki Haley, Kansas Gov. Sam Brownback, and Arkansas Gov. Asa Hutchinson.

But those aren't translating into ballot victories. Rubio has just 151 delegates, while front-runner Donald Trump has 384 of the 1,237 needed to secure the party nomination. 

Analysts have pointed to Florida and Ohio, which both have winner-take-all primaries, as the potential turning point for Ohio Gov. John Kasich and Rubio, both of whom position themselves as the mainstream alternative to the more polarizing Trump and Texas Sen. Ted Cruz. Home-state victories could reenergize voters and donors, while losses would be particularly humiliating. In Florida, where polls show a lead of almost 20 points for Mr. Trump, Team Rubio has been working overtime to avoid a Waterloo on March 15.

But even without a big win in Florida, Rubio could still force a contested convention in July. 

If Governor Kasich, Senator Cruz, and Rubio's bitter rivalry can siphon enough votes away from Mr. Trump, preventing him from reaching 1,237 delegates, they can try their cases at a brokered convention. Right now, that's just barely possible: the three combined have 488 delegates, versus Trump's 384. 

"Saturday proved that Trump can be contained and even beaten," GOP strategist Scott Jennings told The New York Times after Super Saturday primaries in Kansas, Kentucky, Maine, and Louisiana (where Rubio finished third in all but Maine, where he was came in fourth). "The question is whether the field is going to allow for it moving forward. The most likely scenarios remain that Trump gets enough before Cleveland, or nobody does. The latter moved a little closer to realistic Saturday."

Whether Trump or Rubio are better prepared for the "long slog" ahead, as Rubio predicted Sunday, may depend on changing not just their tune, but their methods.

Trump's bombastic campaign may have difficulty picking up mainstream voters, although his Super Tuesday victories challenged the "fringe candidate" notion his rivals had cherished. Rubio's campaign, on the other hand, has staked itself on "late deciders," and strategies meant to swoop in and convince them in the last week before a primary, as The Washington Post reported. But it could be too late, on the calendar or the budget, to build the in-state campaign machines needed to persuade more voters earlier on. 

And although Rubio's optimistic messaging may be his strongest distinction among the GOP field, he may need to more clearly signal how, or whether, the policies behind his "Don't give into the fear" attitude are really so different from his rivals'. 

"I felt I had a dog in the fight, and it hurt me personally when I thought we were going to win," Oklahoma Sen. James M. Inhofe, who had endorsed Rubio before his disappointing third-place primary, told the Post. "The thing is, when Rubio was there, the enthusiasm was so great, better than the others. He had a great reception. If everything had been equal in terms of appearances and organization, he would have won Oklahoma."