“I don’t think Marco would want to run against Jeb in a primary, the way their relationship is,” J. C. Planas, a former South Florida legislator who has worked with both men, told me. “But you never know, just because of the way things work. If Jeb became president, more than likely it means Marco probably never would.”

Florida Republicans, whose state has never produced a president, approach the prospect of their running against each other somewhere on the spectrum between disbelief and dread. “It’s hard for me to imagine, maybe because I so badly don’t want [it to happen],” says someone who knows them both. “I cannot fathom anybody in Marco’s orbit doing anything to harm Jeb Bush, or vice versa.” …

The two men are not as close today as they were in their Tallahassee days. Rubio no longer relies on former Bush staffers to fill out his team. With the exception of a few key players, there isn’t significant overlap between the two camps. And reporters have been busy looking for any sign of tension between them. In December, they seized on a comment from Bush’s youngest son, Jeb Jr., who claimed that Rubio had to “actually execute and get something done rather than just talking.” (In an e-mail, Jeb Jr., who is considering his own run for office in Florida, denied any tension with Rubio.)