Bill Weld, the vice-presidential hopeful on the Libertarian ticket, said Sunday that he sees a stark contrast between the candidates on the top of the two major-party tickets.

Republican presidential nominee Donald Trump is “totally unfit to be president of the United States,” Weld, a former Republican governor of Massachusetts, said on CNN’s “State of the Union.”

Democrat Hillary Clinton, by contrast, is a “perfectly reputable, professional, responsible candidate for president of the United States,” he said.

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Weld urged support for his ticket, headed by Gary Johnson, a former Republican governor of New Mexico, but added: “I do see a big difference between the two other candidates, Mr. Trump and Mrs. Clinton.”

Both the Libertarian and Green Party tickets remain mired in the single digits nationally, though they could factor into the outcome in some tight battleground states Tuesday, including New Hampshire, where some polls show the Johnson-Weld ticket drawing about 10 percent of support.

Weld has said in other recent interviews that he is willing to vouch for Clinton, and on Sunday he acknowledged the high stakes in the race between the two major-party candidates.

“I think people are going to look back on this election and really reflect on the vote that they took,” Weld said. “And I think it's a year when people have to think for themselves and cast a vote of conscience.”