Former presidential candidate Mitt Romney may be getting closer to endorsing a candidate in the 2016 race, and it won't be Republican Donald Trump.

Libertarian party nominee Gary Johnson has spoken with Romney about gaining his public support.

"I think he's considering the possibility of doing this," Johnson told CNN's Wolf Blitzer Thursday in Philadelphia. "Actually endorsing the two of us."

Johnson is running for president alongside his vice presidential candidate Bill Weld, who like Romney is a former Republican governor of Massachusetts. Weld joined Johnson in Thursday's interview.

"He's thinking about it, Wolf, and I don't want to press the point unless and until we get to 15 percent [support in national polls], because then I think the case for it is overwhelming," Weld said. "A couple of the Bushes have already come out in support of us, we're very hopeful that Gov. Jeb Bush might see his might see his way clear to supporting the ticket. But whether or not they do, we're creeping up on that figure that will get us in the debates.

"I can almost guarantee you, if we get to 15, we're gonna get to 20 percent. And at that point, we are extremely dangerous as the ticket."

Presidential candidates need to have at least 15 percent support in national polls in order to participate in debates.

Romney told CNN last month that he does not plan to vote for either Trump for Democrat Hillary Clinton in November.