Changes

Kevin Nicholson, a former Democrat, joined the Republican primary on July 26, 2017, running against incumbent Senator Tammy Baldwin.

According to the Federal Election Commission, Richard Uihlein contributed a total of $19,068,500 to super PACs, Hybrid PACs and Historical Soft Money Party Accounts while his wife Liz has contributed $2,525,000 (As of July 22, 2016).<ref name="Uihlein search"/> Uihlein is the fourth largest contributor to outside spending groups in the 2016 election cycle, according to the ''Center for Responsive Politics'', spending a total of $13,658,500 in disclosed outside spending.<ref> Center for Responsive Politics, [https://www.opensecrets.org/outsidespending/summ.php?cycle=2016&disp=D&type=V 2016 Top Donors to Outside Spending Groups], ''opensecrets.org'', accessed April 27, 2016.</ref> (As of July 22, 2016).