On Friday, the group endorsed Matt Bevins, a Louisville businessman who is mounting a primary campaign against Senate Minority Leader Mitch McConnell (R-Ky.). The organization is also backing Mississippi state Sen. Chris McDaniel against six-term incumbent Sen. Thad Cochran (R-Miss.).
The spending has drawn the ire of some Republicans, including National Republican Senatorial Committee communications director Brad Dayspring.
"Conservatives who give to SCF do so for right reasons. Sadly biggest beneficiary of SCF tactics has been Harry Reid, not conservative cause," Dayspring tweeted on Friday.