Sen. Marco Rubio (R-FL) is warning party leaders that they may be playing with fire if they take the nomination away from frontrunner Donald Trump even if he doesn’t seal 1,237 pledged delegates walking into the Republican National Convention.

It’s still an open question as to whether Trump will secure enough guaranteed support before the convention to wrap up the nomination by June 7, or if he will need to work with unbound delegates to get to a majority at the convention.

While the looming potential struggle has haunted party leaders, Rubio—one of Trump’s chief rivals before he dropped out of the race after losing him home state of Florida to Trump by more than 15 points—is warning that even if Trump doesn’t get all the way there it’s unwise for the GOP to shun the voters.

In an interview with local Miami radio host Jimmy Cefalo, Rubio rejected Trump’s claims that the nomination system is “rigged” but did argue that taking the nomination from Trump if the business mogul falls just short of a majority of delegates could divide the party. It’s a marked shift in tone from Rubio, and yet another sign that party leaders could be open to backing Trump after all.

“I do think it’s valid to argue to delegates,” Rubio said before adding:

Look let’s not divide the party. You have someone here who has all these votes, very close to get 1237, let’s not ignore the will of the people or they’re going to be angry. Delegates may decide on that reason that they decide to vote for Donald Trump but if they don’t it’s not illegitimate in any way.

Cefaldo asked in a follow-up whether Rubio would support Trump as the nominee.

“I’ve always said I’m going to support the Republican nominee, and that’s especially true now that it’s apparent that Hillary Clinton will be the Democrat nominee,” Rubio said.

Hillary Clinton would be a disaster for America, she really would. I think she’s got a lot of ethical questions surrounding her campaign. I think she was not a very good Secretary of State, and quite frankly she’s a candidate who looks backwards, America needs to turn the page and look to the future.

Rubio’s seeming shift in tone comes shortly after several of his supporters who are D.C. delegates or alternates told Breitbart News that they were warming to the idea of a Trump nomination especially if Rubio played a significant role in his team.