"I can't vote for Hillary Clinton and I can't vote for Donald Trump, and it breaks my heart," Mr. Bush said in an interview that aired on MSNBC Monday evening. "This is my the first time in my adult life I'm confronted with this dilemma."

"A lot of the governors, I would have been very comfortable with," Mr. Bush said. "John Kasich I thought ran a great campaign, and [Marco] Rubio, [Ted] Cruz. There are a lot of people. The bar's not that high for me. I'm not suggesting that you have to be a perfect candidate."

Mr. Bush was one of the more aggressive critics of Mr. Trump during the 2016 GOP presidential primary race, but he dropped out of the race after a disappointing finish in South Carolina.

"This is a decision that's painful for me," he said. "I love my country like everybody else does, and I see us languishing at a time when we should just be leading the world."