The parents of Republican US Senate candidate Kevin Nicholson have donated the maximum amount to the campaign of their son's Democratic rival, Tammy Baldwin.
Mr Nicholson is in a primary battle against fellow Republican Leah Vukmir, with the winner advancing to take on Ms Baldwin in the autumn.
Federal records show Mr Nicholson's parents, Michael and Donna, each gave $2,700 to Ms Baldwin in December.
He is a former Democrat, but his parents have a long history of donating to Democratic candidates.
Mr 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."