Mary M. Kolar and C.J. Terrell will face off April 2 for the lone position up for grabs on the 37-person Dane County Board of Supervisors.
Both candidates submitted valid nomination papers by Monday's deadline, according the county clerk's office.
Kolar is a retired U.S. Navy officer and director of public operations at the Madison Museum of Contemporary Art and has McDonell's endorsement. She announced her candidacy last November.
Adam Brabender had declared his candidacy and submitted his campaign finance registration statement and statement of economic interest but did not file nomination papers Monday, so his name will not appear on the spring ballot.