The super-PAC for the nation’s largest labor federation is going on the attack against the Republican challenger to Ohio Sen. Sherrod BrownSherrod Campbell BrownPence knocks Sherrod Brown in Ohio, boosts Renacci On The Money: Trump imposes B in tariffs on China | China blasts 'fickle' Trump, promises payback | Trump to name consumer bureau director next week Bank regulator faces backlash over comments on racism MORE (D) with a parody of the famous “Witness” ads for LeBron James. 

Workers’ Voice, the super-PAC of the AFL-CIO, is spending about $100,000 on the ad blitz against Ohio state Treasurer Josh Mandel (R).

Workers’ Voice will run ads against the GOP Senate candidate all this week on the online homepages and sports pages of the Cleveland Plain Dealer and the Akron Beacon Journal. The ads take issue with campaign contributions to Mandel that have reportedly fallen under FBI investigation.

Parodying Nike’s “Witness” ads for James — the former Cleveland Cavaliers star who is now playing for the Miami Heat in the NBA finals — the ads direct visitors to a Workers’ Voice webpage that asks people to “witness the Mandel investigation.” 

“In the weeks since it became public that the FBI was investigating campaign contributions made to Josh Mandel, he still refuses to come clean on a few basic questions surrounding the tainted campaign cash,” reads the webpage. 

It directs users to sign a petition that asks Mandel to answer questions about the investigation.

The ads will also appear on Facebook and Twitter and are tied to Google and Bing searches about the NBA finals, as well as about James.

The battle between Brown and Mandel will a key race for labor this election. Brown is a staunch advocate of unions and has been targeted by several conservative-leaning groups with outside ads during the campaign so far.