From the source -
Langan, of Ashwaubenon, made the announcement during a news conference Wednesday morning at Brown County Democratic Party headquarters in Green Bay, and hitched his run to efforts by Wisconsin Democrats to seize control of the state Senate. Republicans now control the body, 19 to 14; a gain of three seats by Democrats would put them in control.
...Langan faces a big challenge in running against Cowles, who's served in the Senate for over 24 years and represents a district all three of whose Assembly members are Republicans. The Cowles recall effort was the last one to collect enough signatures to force an election. The state Government Accountability Board is now in the process of vetting the signatures.