A pair of leading conservative groups is heaping a lot of attention on Sen. Mark Pryor (D-Ark.), one of the cycle's most vulnerable incumbents. The interest in Pryor's seat comes as Rep. Tom Cotton (R), a rising conservative star, has emerged as potential challenger.

Cotton is an Iraq War veteran and conservative darling whose 2012 House bid was backed by the anti-tax Club For Growth, one of two conservative groups that commissioned polling on the race that was released Tuesday. The polling data, which Basswood Research collected, show Cotton leading Pryor, 43 percent to 35 percent. Cotton hasn't ruled out a Senate run, and recently said he probably won't  come to a decision for some time.

The release of the polling data comes three weeks after the Club went up on the air with six-figure TV ad buy slamming Pryor's record. The ad made no mention of Cotton, but it was a notable purchase coming so early in the cycle.

"As I’ve said before, the Club for Growth PAC would strongly consider supporting Congressman Cotton if he chose to try and take his free-market principles to the United States Senate, but as far as we know he hasn’t made a decision yet," Club For Growth spokesman Barney Keller said, repeating his stance after the launch of the anti-Pryor ad.

In other words, the group certainly wouldn't mind seeing Cotton run.

But acitivists may not learn of the congressman's plans are anytime soon. "There’ll be a time later for me to think more seriously about politics, but I don’t anticipate that’ll be for many months,” Cotton told Post Politics last week at CPAC. A Cotton spokeswoman said his mindset hasn't changed since that conversation.

Matt Hoskins, executive director of the Senate Conservatives Fund, the second group that commissioned the polling, said his organization has not identified a preferred candidate in Arkansas yet, but would consider backing Cotton if he runs.

"We don't have a favorite in this race at this point," Hoskins said. "We are acting early because we want to defeat Mark Pryor. We hope a strong conservative challenger will emerge but there is no guarantee that will happen."

Indeed, the internal polling data the groups released (which you can check out here) wasn't just about Cotton. It showed Pryor's favorability falling deeper underwater and an increasing perception that he was siding too much with President Obama — data apparently meant to reflect the efficacy of the Club's TV ad.

The Senate Conservatives Fund also recently went up with a radio ad targeting Pryor.

Still, it's notable that the released data only included the Pryor-Cotton match-up. Cotton's not the only Republican in the conversation. Lt. Gov. Mark Darr (R) appears poised to make a bid for Pryor's seat.

Hoskins didn't rule out backing Darr, noting that his group has vetted neither him nor Cotton.

For his part, Pryor kicked off his campaign Saturday, with an assist from Bill Clinton. The second-term senator is one of the most vulnerable Democrats facing reelection next year, especially given his state's increasingly red hue.

Senate Democrats' campaign arm responded to the prospect of a Cotton Senate candidacy by noting that the Republican is still very new to Congress.

"The people of Arkansas elected Tom Cotton five minutes ago. If he already deems himself worthy of a promotion, then he is in for a lot of disappointment," said Democratic Senatorial Campaign Committee spokesman Matt Canter.

National Republican Senatorial Committee spokesman Brad Dayspring would not comment on specific Republican candidates. He pointed to Pryor's record as a reason for Republican optimism in Arkansas.

"Polling shows that Mark Pryor is going to have serious problems in Arkansas defending his voting record and support for President Obama's liberal agenda,"  Dayspring said.