Outside spending against Democratic incumbent Sen. Tammy Baldwin of Wisconsin has so far exceeded the combined outside spending against the other 21 Democratic Party senators up for reelection in 2018 by a factor of 5.
There has been $3.1 million in outside spending against Baldwin, and about $532,000 against the other Democratic incumbents combined. (Another $6,214 has been spent against Vermont Sen. Bernie Sanders, who caucuses with Democrats).
Baldwin is one of 10 Senate Democrats running for reelection in states that President Donald Trump carried in 2016. Nearly all of the conservative-aligned outside spending has targeted Baldwin, however.
Baldwin has been a senator since 2013 and was formerly the representative for Wisconsin's 2nd Congressional District.
Among Democratic senators in Trump-carried states, the next largest amount was about $47,000 targeting West Virginia Senator Joe Manchin. About $42,000 has been spent against Missouri Senator Claire McCaskill, according to FEC data.
"Outside spending" refers to political expenditures by groups or individuals not coordinated with candidates' fundraising committees.
On the Republican side, outside spending against GOP Senate candidates is even higher.
In the 2018 cycle, about $4.7 million of the roughly $5.2 million -- or around 90 percent -- of outside spending against all Republican candidates for the Senatehas targeted Alabama's Republican Senate candidate Roy Moore. All but about $295,000 of the $4.7 million targeted Moore before the Republican primary in September. Outside spending after the primary has come from two groups, The Advocacy Fund and Highway 31.
Nicholson is a former Democrat who once worked for the Democratic National Committee and even spoke at its 2000 convention.
Uline Inc, a Wisconsin-based shipping supply company owned by Illinois-based conservative donor Richard Uihlein, gave $3.5 million to the pro-Nicholson super PAC Solutions for Wisconsin. Uihlein's investments also include several resorts, spas and restaurants in the state.
Solutions for Wisconsin, in turn, has contributed $1.5 million to Americas PAC and Restoration PAC, which represent the second and third largest outside spenders opposing Baldwin. Uihlein also gave $250,000 directly to Americas PAC. He is the chief donor to a super PAC that has funded ads benefiting Moore as well, The Daily Beast reported.
Two advisors Nicholson is replacing on his campaign are taking positions at Solutions for Wisconsin.
So far in the 2018 cycle, Uihlein has funded roughly $6.1 million in outside spending, all of which went toward conservative groups.
The outside spending group that has spent the most against Baldwin is Freedom Partners Chamber of Commerce, a politically active nonprofit that serves as the fundraising hub of the donor network spearheaded by billionaire industrialists David and Charles Koch.
Freedom Partners has spent around $1.7 million to defeat Baldwin, and as a 501(c)(6) trade association, it is not required to disclose its donors.