Wisconsin Constitution Art. V § 3. Election

Section 3. The governor and lieutenant governor shall be elected by the qualified electors of the state at the times and places of choosing members of the legislature. They shall be chosen jointly, by the casting by each voter of a single vote applicable to both offices beginning with the general election in 1970. The persons respectively having the highest number of votes cast jointly for them for governor and lieutenant governor shall be elected; but in case two or more slates shall have an equal and the highest number of votes for governor and lieutenant governor, the two houses of the legislature, at its next annual session shall forthwith, by joint ballot, choose one of the slates so having an equal and the highest number of votes for governor and lieutenant governor. The returns of election for governor and lieutenant governor shall be made in such manner as shall be provided by law.