Pat McGeehan, a former West Virginia state delegate, announced his run for Senate via Twitter on Tuesday, saying he's "running to win."
"I think West Virginians deserve a candidate that will truly represent their views. I am a pro-life, pro-gun, pro-coal conservative that believes government today is too overreaching. That is why I am running for U.S. Senate in West Virginia," he wrote in an accompanying statement.
Capito announced her intentions to pursue retiring Sen. Jay Rockefeller's (D-W.Va.) seat before he announced his decision not to run for another term, and has thus far been unopposed.
But within hours of her announcement, conservatives blasted her, charging her record is too liberal and expressing an openness to backing a primary challenger.
It's unclear whether McGeehan could be that challenger, as he has no experience running for federal office and lost two state Senate bids. But Chris Chocola, president of the conservative Club for Growth, one of the groups that blasted Capito when she announced her run, tweeted at McGeehan asking to meet.
"@McGeehan4WV you should come in and interview with us," he tweeted.
McGeehan re-tweeted Chocola, but according to a spokesman for the group, he hasn't yet set up a meeting.
With the backing of well-funded conservative groups like the Club for Growth, a primary challenger could create a headache for Capito. But she recently announced raising $915,000 for her bid, and any candidate would have to begin soon to be able to catch up to her head-start.
Republicans are favored to win the seat in the red-leaning state, and Democrats have yet to front a candidate.
Potential contenders include Secretary of State Natalie Tennant, attorneys Ralph Baxter and Nick Preservati, as well as former Kentucky Democratic Party Chairman Mike Callaghan. Rep. Nick Rahall (D-W.Va.) has not ruled out a bid, but looks increasingly unlikely to run.