Wisconsin Republican Senate candidate Kevin Nicholson said he questioned the “cognitive thought process” of military veterans in the Democratic Party.

Speaking in an interview on WTMJ-AM, Nicholson, who is running to challenge Democratic Sen. Tammy Baldwin, defended his claim that his service in the Marines is a conservative value.

Nicholson has been met with skepticism by some Republicans in the past given his previous tenure as president of the College Democrats of America.

“And just because some people that don’t call themselves conservatives and don’t always act conservative do something conservative,” he said, using the example of 2004 Democratic presidential nominee John Kerry serving in the Navy. “That doesn’t mean that that’s not a conservative thing to fundamentally protect and defend the Constitution.”

The Democratic Party has abandoned the U.S. Constitution, Nicholson said.

“Those veterans that are out there in the Democrat party, I question their, 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,” he said.

Republican strategist Alex Conant, an adviser for a PAC that supports Nicholson’s primary opponent state Sen. Leah Vukmir, tweeted that Nicholson’s remarks could cost Republicans Wisconsin’s seat.

Candidates saying stuff like this is how the GOP loses winnable races https://t.co/bsac7J9rhR

— Alex Conant (@AlexConant) May 3, 2018

Democratic House candidate Tom Palzewicz, a Navy veteran challenging Rep. Jim Sensenbrenner, criticized Nicholson’s statements.

“For almost every member of the Armed Forces, for veterans, for military families, country comes before party, but apparently not for Kevin Nicholson. He should be ashamed,” he said.

Inside Elections with Nathan L. Gonzales rates Wisconsin’s senate race “Tilt Democratic.”