Freshman Rep. Tom Cotton (R-Ark.) has collected a major endorsement from a conservative PAC the day after his Tuesday entry into Arkansas's Senate race against top GOP incumbent target Sen. Mark Pryor (D-Ark.), and another top right-wing group says it's "open" to backing him.

In a release, the Club for Growth hailed Cotton as a "taxpayer hero and a fighter against the Obama agenda." It vilified Pryor for being Obama's "greatest ally in Arkansas" for his support of Obamacare, the stimulus package and the Wall Street bank bailout.

The PAC concurrently announced a new ad buy against Pryor, who has been getting barraged on the airwaves early in the 2014 campaign.

Also Wednesday morning, the Senate Conservatives Fund, which was formerly allied with ex-senator Jim DeMint (R-S.C.), said it would look at also backing Cotton's candidacy.

The SCF said it "is open to endorsing U.S. Representative Tom Cotton (R-AR) for the U.S. Senate if he leads on the big issues and excited the grassroots in Arkansas."

The Club for Growth and SCF have led efforts in recent years to support conservative primary opponents to establishment-backed candidates. Cotton, though, appears to be getting support from both sides of a divided party.

Emphasizing more their commitment to defeat Pryor, SCF cited the $400,000 they spent "educating voters about Senator Mark Pryor's liberal record before he could attempt to reinvent himself."

"We kicked the stool out from under Mark Pryor earlier this year and we don't think he will be able to get up off the ground," said SCF executive director Matt Hoskins.

Cotton, a 36-year-old war vet, announced his bid Tuesday evening, and Pryor's campaign has already launched a small ad buy seeking to define him.