(CNN) Wisconsin GOP Senate candidate Kevin Nicholson said in a radio interview on Wednesday that he questions the "cognitive thought process" of veterans who vote Democratic, arguing that their military service contradicts their political views.

Asked by host Steve Scaffidi on the local station WTMJ about Republican primary opponent Leah Vukmir's suggestion that her record as a Republican state senator should mean more to conservative voters than his military experience, Nicholson argued that to serve in the military is fundamentally conservative.

"And just because some people that don't call themselves conservatives and don't always act conservative do something conservative -- like, let's talk about John Kerry -- and signed up to serve this country, that doesn't mean that that's not a conservative thing to fundamentally protect and defend the Constitution," Nicholson said. "Because I'll tell you, the Democrat party has wholesale rejected the Constitution and the values that it was founded upon. So I'll tell you what: Those veterans that are out there in the Democrat party, I question their cognitive thought process because the bottom line is, they're signing up to defend the Constitution that their party is continually dragging through the mud."

Nicholson went on to tout "my time as a husband, my time as a father," as well as the endorsements of Texas Sen. Ted Cruz and Utah Sen. Mike Lee as further conservative credentials.

Nicholson's military service has been a focal point of his campaign to be the GOP nominee to unseat Democratic incumbent Tammy Baldwin in November, as has his journey from being a member of the Democratic Party as a younger man to becoming a Republican. Nicholson was president of the College Democrats of America and spoke at the 2000 Democratic National Convention. He later joined the Marines and told Politico in September 2017 that his deployment to Iraq in 2007 was key to changing his political views, saying he was "livid" with Democrats for calling the war a failure.

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