BOISE -- U.S. Republican Rep. Mike Simpson told KTVB Wednesday that he will not vote for his party's candidate, saying he does not believe Donald Trump deserves to be in the White House.

But Simpson said he won't back Trump's biggest rival Hillary Clinton either.

"On one hand, you've got someone acting like a high school kid, and on the other hand you've got someone that would have to get a waiver to get a national security clearance to be president of the United States," he said. "I can't vote for Hillary- wouldn't vote for Hillary - and I don't think Donald Trump is fit to be president."

MORE: Otter, GOP stand by Trump after lewd comments

Simpson said he is looking at third-party candidates, but has not yet decided who will get his vote.

He expressed disgust at the choice presented by the major-party candidates.

"It's like we're being offered hemlock or strychnine and the debate is which one's the least painful," he said.

The congressman's refusal to back the Republican presidential candidate is a departure from the stance of his colleagues: Sen. Jim Risch, Sen. Mike Crapo and U.S. Rep. Raul Labrador have all said they will cast their ballots for Trump.

RELATED: Crapo says he will vote for Trump despite pulling endorsement

Simpson, who did not endorse Trump, called his vulgar comments about women the "final straw."

He said he wants to see Americans stand up for decency and civility, and demand more from the political process.

"At some point in time, The American people have to say 'we deserve better than this, we deserve a better race than this and we deserve better candidates than this - people who don't act like children.'"

Simpson made the comments during a taping of of KTVB's Decision 2016 Viewpoint that will air Sunday, Nov 6. The segment will include his opponent, Democrat Jennifer Martinez.