(CNN) Just months after Republican Kevin Nicholson announced his bid to unseat incumbent Democratic Sen. Tammy Baldwin in 2018, his own parents donated the legal maximum to her primary campaign.

Nicholson announced last July that he would seek the Republican nomination for US Senate in Wisconsin. A Federal Election Commission filing by Baldwin's campaign dated February 5 and available online shows that each of Nicholson's parents, Donna and Michael, donated $2,700 to Baldwin in December 2017. FEC rules stipulate that those donations are the maximum Nicholson's parents can donate to Baldwin during the primary election. They can donate up to that amount again during the general election.

Their donations are not necessarily out of character: Nicholson has said on the campaign trail that he comes from a Democratic family and, as the Milwaukee Journal-Sentinel reported in November , his mother has donated thousands of dollars over the years to Democratic organizations and candidates, including hundreds to Baldwin.

However, the contributions are the first his parents have given to Baldwin since Nicholson announced his candidacy to try to oust the senator.

In a statement to CNN, Nicholson said, "My parents have a different worldview than I do, and it is not surprising that they would support a candidate like Tammy Baldwin who shares their perspective."

Read More