McConnell-linked PAC threatens to blackball conservatives who challenge 2020 GOP incumbents: report
Senator Mitch McConnell of Kentucky speaking at the 2013 Conservative Political Action Conference (CPAC) in National Harbor, Maryland. (Gage Skidmore/Flickr)

On Friday, Politico reported that the National Republican Senatorial Committee (NRSC), along with the Mitch McConnell-affiliated Senate Leadership Fund super PAC, adopted a "zero-tolerance policy" to blackball consulting firms or Republican strategists who work for people mounting primary challenges to GOP incumbents.

The news came after a report that the Club for Growth, an anti-tax group that is heavily involved in Republican politics, is trying to recruit Rep. Mark Walker (R-NC) to challenge Sen. Thom Tillis (R-NC).

Tillis, who was elected in the 2014 cohort that flipped the Senate to the GOP, is broadly considered to be one of the most vulnerable members standing for re-election in 2020. He angered President Donald Trump's allies earlier this year when he wrote an editorial supporting the Democrats' resolution to block the national emergency declaration to divert military funds to the president's border wall. Tillis later flip-flopped and voted against the measure, but that did little to quieten the discontent of right-wing insurgents.

Already, GOP pollster John McLaughlin has come under fire for working with Garland Tucker, a businessman who is already planning to challenge Tillis. McLaughlin eventually bowed out of the job.