Wisconsin Constitution
Article IV - Legislative
Section 5 - Senators, how chosen.

[As amended Nov. 1881 and Nov. 1982] The senators shall be elected by single districts of convenient contiguous territory, at the same time and in the same manner as members of the assembly are required to be chosen; and no assembly district shall be divided in the formation of a senate district. The senate districts shall be numbered in the regular series, and the senators shall be chosen alternately from the odd and even-numbered districts for the term of 4 years. [1880 J.R. 9S, 1881 J.R. 7A, 1881 c. 262, vote Nov. 1881; 1979 J.R. 36, 1981 J.R. 29, vote Nov. 1982]