Evan McMullin, who launched an independent presidential bid Monday, repeatedly called GOP nominee Donald TrumpDonald John TrumpJustice Department preparing for Mueller report as soon as next week: reports Smollett lawyers declare 'Empire' star innocent Pelosi asks members to support resolution against emergency declaration MORE “weak” and said he’s “ensuring” that Democrat Hillary ClintonHillary Diane Rodham ClintonFBI’s top lawyer believed Hillary Clinton should face charges, but was talked out of it Harris adds key Clinton aide, women of color to 2020 campaign: report Democrats more likely Trump's foil, than to foil Trump MORE wins the White House this fall.

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During an interview with ABC’s Tom Llamas, the former CIA agent and House Republican Conference policy adviser questioned whether Trump has the physical capacity to run for president.

“It’s clear to me that he is a weak candidate,” McMullin said during the interview. “Trump is weak, and in fact, I question whether he actually has the stamina to complete the race.”

“He is ensuring that Hillary Clinton wins this election,” he continued.

"I think they would both be absolutely terrible,” McMullin added.

McMullin officially launched his presidential bid earlier on Monday, criticizing both major parties’ nominees. MSNBC’s Joe Scarborough first reported the news of McMullin’s candidacy and said he’d likely try to get on the ballot in 20 to 30 states.

McMullin continued to rail against Trump and pointed to the real estate mogul’s recent remarks about the Muslim parents of a U.S. Army captain killed in Iraq. Khizr Khan — whose son, Army Capt. Humayun Khan, was killed by a suicide bomber in 2004 — delivered a scathing rebuke of Trump at the Democratic National Convention in Philadelphia.

"Donald Trump does not care about anyone but himself," McMullin said, adding that Trump’s comments about the Khans show he’s “inhuman.”

"I do believe he is a fraud and a con man and that’s not something I say lightly," McMullin said.

McMullin also offered a sharp rebuke of Clinton and said her use of a private email server while serving as secretary of State illustrates that "she believes that she's unaccountable to the American people."

He said he wished a candidate with higher name recognition declared a challenge against Trump “many, many months ago.”

McMullin said an individual asked him to run but wouldn’t disclose the person’s identity. He also noted that he hasn’t talked to 2012 GOP nominee Mitt Romney, Republican National Committee Chairman Reince Priebus or House Speaker Paul RyanPaul Davis RyanThe Hill's 12:30 Report: Sanders set to shake up 2020 race McCabe: No one in 'Gang of Eight' objected to FBI probe into Trump Unscripted Trump keeps audience guessing in Rose Garden MORE (R-Wis.) about his candidacy.