Was Mandela Barnes’ complexion darkened in a mailer against him?

A mailer produced by the Wisconsin Republican Party appears to use a filter to darken one side, which contains a picture of Wisconsin Lt. Gov. and Democratic U.S. Senate candidate Mandela Barnes. Barnes' complexion in the mailer is significantly darker than how it appears in the original photo. The other side, depicting the campaign of Barnes' opponent, Republican U.S. Sen. Ron Johnson, is not darkened.

Gerard Randall of the Wisconsin Republican Party did not explain the darkening of the photo. Randall, who is Black, responded by pointing out that the main accusers were two white Democratic state lawmakers. 

Supporters of Barnes have accused Republicans of using racist tropes in their ads, including placing Barnes against graffiti backdrops and labeling him as "different" and "dangerous" alongside other Democratic lawmakers of color.

None of the ads in question was made by the Johnson campaign itself. Barnes' campaign called the ads "outright lies" but did not address the racism component.