Photo Evan McMullin, a former C.I.A. official and a Republican who passionately opposes Donald J. Trump, will file papers to run for president as an independent candidate, according to two people briefed on his plans.

Mr. McMullin, who until recently worked on policy development with the House Republican conference, has missed the ballot-access deadlines in more than two dozen states.

In a statement provided by an aide, Mr. McMullin said, “In a year w Americans have lost faith in the candidates of both major parties, it’s time for a generation of new leadership to step up.”

“It’s never too late to do the right thing, and America deserves much better than either Donald Trump or Hillary Clinton can offer us,” his statement said.

Mr. McMullin is said to be backed by the group Better for America, which earlier this year began an effort to get on the ballot in as many states as possible, with the hopes of drafting a candidate.

Rick Wilson, a Republican consultant and Trump foe, is the main strategist on the effort.

Polling shows that Mr. Trump’s support in Utah is very low for a Republican presidential candidate, and it has particularly suffered amid his battles against Mr. Romney, a Mormon who was the Republican nominee for president in 2012.If Mr. McMullin is competitive now else but Utah, he still could nonetheless have an impact on the race: Mr. Trump cannot win the presidency without holding the states that Mr. Romney won, his aides have concluded.

That Mr. McMullin has a national security background makes him a more appealing option, potentially, to Republicans or conservatives who cannot bring themselves to support Mr. Trump, but also strongly dislike Mrs. Clinton, the Democratic nominee.