Mitt Romney has closed the book on his efforts to woo an independent challenger to take on presumptive GOP presidential nominee Donald Trump Donald John TrumpUS reimposes UN sanctions on Iran amid increasing tensions Jeff Flake: Republicans 'should hold the same position' on SCOTUS vacancy as 2016 Trump supporters chant 'Fill that seat' at North Carolina rally MORE and likely Democratic nominee Hillary Clinton Hillary Diane Rodham ClintonJeff Flake: Republicans 'should hold the same position' on SCOTUS vacancy as 2016 Momentum growing among Republicans for Supreme Court vote before Election Day Warning signs flash for Lindsey Graham in South Carolina MORE.

ADVERTISEMENT

Yahoo News reported that the 2012 GOP nominee, who convened a high-profile speech bashing Trump and calling for his defeat during the primaries, has stopped taking action on finding an independent candidate and won’t run himself.

“He thinks someone should run. That’s his role. That’s the beginning and end of it,” a Romney adviser told Yahoo.

“Is he organizing it? No. But he has talked to people who have thought about it.”

Another ally told Yahoo that Romney "is not now engaged in an effort to recruit a third-party candidate."

The news comes after a series of reports that Romney had reached out to Republicans Ohio Gov. John Kasich and Sen. Ben Sasse (Neb.), among others. But those efforts have so far not come to fruition, and Kasich has ruled out a bid after ending his presidential campaign after losing to Trump in the Indiana primary.

Each day that goes by makes the organizational challenge even greater as state ballot deadlines near.

And Erick Erickson, the founder of the conservative RedState.com who has also worked to find an independent candidate, told The Hill last week that the operation would need at least $250 million behind it.