Rubio surveys newspapers featuring his photo aboard his campaign bus following a rally in the Villages, Fla., on March 13. (Carlo Allegri/Reuters)

As Sen. Ted Cruz was addressing the Indiana Republican Party’s spring dinner last week, his father was on a secret mission to Puerto Rico.

Rafael Cruz, a pastor who is one of his son’s most popular surrogates, was meeting privately at a home in Dorado with some of the island’s 23 delegates to the Republican National Convention — all of whom are still bound to a presidential candidate who got out of the race more than a month ago.

That’s Sen. Marco Rubio (R-Fla.). His White House bid may be over, but his potential to keep the GOP nomination from going to Donald Trump lives on.

Rubio — berated on the campaign trail by Trump as “Little Marco” — still has scores of convention delegates who are required to vote for him on the first ballot, and who could go anywhere on the second and beyond.

The senator suspended his bid more than a month ago, on the night he lost his home state of Florida to Trump.

Tracking the race to the Republican nomination

But — in part at the request of Cruz’s campaign — he has done what he can to hang on to the 171 delegates he won in 21 states and territories. That is more than Ohio Gov. John Kasich has, even now.

Rubio sent letters to state parties noting that his decision to suspend his campaign should not be interpreted as a release of his delegates. Whether they remain bound to him, however, varies according to the rules of individual states, how they are interpreted by party officials, and the inclinations of GOP leaders in those states.

The best estimates now suggest that Rubio can count on at least 50 delegate votes on the first ballot and may have to relinquish 30 to 40. The remainder — as many as 81 — are in limbo.

Rubio’s delegates could be crucial should Trump fall short of the 1,237 delegates he needs to take the nomination on the first ballot.

They also give him leverage, although those close to him say he is not sure what he would do with it.

“It’s about keeping doors open — to step through and do what, who knows?” said one adviser, who spoke on the condition of anonymity because the topic is sensitive.

Rubio declined a request for an interview.

He has insisted that he has no interest in being someone else’s pick for vice president or in putting his name back in the presidential mix, should the convention reach a deadlock.

Asked by Univision in a weekend interview about his plans for his delegates, Rubio said in Spanish: “What I want to see at the convention is for the party to name someone as a candidate who is conservative and who can win. That, and if my delegates can have a role, can play a role in reaching that goal, we’re probably open to that, but we haven’t reached that point yet.

“I really don’t have secret or comprehensive plans about what I’m going to do at the convention,” the senator added. “We’re just keeping those options open in order to be able to contribute in a positive way to the party naming a candidate who is conservative and can win.”

Meanwhile, his delegates have their own ideas about how they might use their clout.

Puerto Rico’s, for instance, plan to vote on the first ballot for Rubio, as their rules require, but say their support in later ones would hinge on one issue: statehood for their island.

“Whoever wants our vote needs to pay attention to our particular issues, as well as our struggle for equality as U.S. citizens. If that’s not taken into consideration, we could care less what the polls say,” said Elias Sanchez, a San Juan lawyer and delegate who co-chaired Rubio’s Puerto Rico campaign.

Rubio endorsed statehood, but of the remaining field, only Kasich has done the same. Cruz and Trump have said they support the “right of self-determination,” which the delegates say is not enough.

That’s why last week’s meeting with Rafael Cruz was appreciated, delegates said, but didn’t seal the deal for the senator from Texas. Ultimately, they plan to vote as a bloc for their second choice, whomever that turns out to be.

In Arkansas, other considerations are in play, as state Republicans prepare to gather next month to pick their 40 delegates — including nine who will vote for Rubio on the first ballot.

Bart Hester, an Arkansas state senator, said that he and others who backed the senator from Florida would like to see his delegate slots filled by seasoned state leaders — ideally the governor, lieutenant governor and GOP lawmakers.

“If we go to a brokered convention, emotions are going to be high. There’s going to be a lot of alternatives,” Hester said. “It’s about being a good steward, to make sure we got people there that have a history of making good decisions and being level-headed people. It’s best for all Republicans involved.”

Rubio does not appear to be exerting much pressure.

In Minnesota, the only state Rubio won, the senator “hasn’t been prescriptive with us at all,” said Jeff Johnson, a Hennepin County commissioner who chaired Rubio’s campaign and now backs Cruz.

Virginia GOP Chairman John Whitbeck said, “We haven’t heard anything other than that letter” from Rubio asking to retain his delegates.

Even without a request from Rubio, Virginia’s rules require its delegates to cast 16 of its 49 votes for Rubio on the first ballot. The same holds true in Minnesota, where Rubio won 17 delegates, and in Tennessee, where he won nine. And in Kansas, where he won six.

But after that, Whitbeck said, “this is all new territory for all of us.”

In D.C., Rubio won 10 delegates, but one of his supporters already has announced her plans for later ballots.

Rina Shah Bharara, who was chosen to vote for Rubio, told Fox News Channel this month that she will vote for Democrat Hillary Clinton if Trump wins the GOP nomination. As if that weren’t awkward enough, the local party is investigating reports that Bharara isn’t even a District resident.

Bharara didn’t return requests for comment. But her situation means that party leaders probably won’t be able to decide what to do about Rubio’s delegates until at least June.

By then, Trump is likely to be the presumptive nominee — or in a spot where Rubio’s delegates could keep the prize just beyond his grasp.