Kevin Nicholson did work for Democrats two years after he said he became disillusioned with the party

MADISON - GOP U.S. Senate candidate Kevin Nicholson Tuesday acknowledged being paid to do work for the Democratic Party in Minnesota in 2002 — two years after he has said he became disillusioned with that party.

Nicholson, a former president of the College Democrats of America as well as a businessman and former Marine, has acknowledged his past ties to the Democratic Party. But in the GOP primary for Senate he hasn't always given a clear timeline for when and how he left the Democratic Party.

For instance, in January 2017 Nicholson told conservative talk radio host Vicki McKenna that, after speaking at the 2000 Democratic National Convention, he left the event "absolutely sure" he wasn't a Democrat.

But the new Federal Election Commission records — first reported on by the Associated Press — show that Nicholson was paid $7,300 in salary and mileage reimbursements by the Democratic Party in Minnesota in 2002.

At a WisPolitics luncheon Tuesday, Nicholson said his critics were making too much of his switch, saying that President Donald Trump, Ronald Reagan and many ordinary GOP voters were once Democrats.

"I always talk about that my whole life is an evolution. I got more conservative with everything I've done from my service in the Marine Corps to my time in business," Nicholson said.

A spokesman for the state Democratic Party said voters can't believe what Nicholson says.

"He clearly has a problem with telling the truth, and all we know for sure is that he'll take on any position his out-of-state billionaire backers tell him to embrace," Brad Bainum said.

The campaign for Nicholson's GOP primary opponent, state Sen. Leah Vukmir of Brookfield, responded by saying she is a "lifelong Republican, and proud of it."

"She has been devoted to stapling yard signs, knocking on doors and working to advance the Republican Party and conservative policies," spokeswoman Jess Ward said of Vukmir.

Nicholson distanced himself Tuesday from attacks by a group supporting him — the Club for Growth — that has called Vukmir a "Republican in Name Only."

"I don't think she's a RINO. I think she's an insider," Nicholson said of Vukmir, calling himself an outsider.

RELATED: Bice: Nicholson's mother gives to Dems as her GOP son tries to oust one

GOP Gov. Scott Walker declined to comment on whether he thought Nicholson was a conservative, saying he would leave that decision to voters. But though the governor has remained neutral in the race, Walker's son Alex and the governor's former campaign manager, Stephan Thompson, have both been working to elect Vukmir.

Vukmir and Nicholson are vying to take on U.S. Sen. Tammy Baldwin, a Democrat, in November.

Also this week, records show a super PAC supporting Vukmir has just over $1 million in cash thanks to $500,000 contributions from both Beloit billionaire Diane Hendricks and from the Metropolitan Milwaukee Association of Commerce.

The Wisconsin Next PAC listed the contributions — both made in the final week of 2017 — in a new Federal Election Commission report.

The two major super PAC's backing Nicholson, Club for Growth Action and Solutions for Wisconsin, said earlier this month they will report ending 2017 with $1.1 million cash on hand designated for the Wisconsin race.

The FEC report for Solutions for Wisconsin is not yet available.