(AP) — Republican U.S. Sen. Pat Roberts may be getting a primary challenge in his bid for re-election.

Milton Wolf is inviting supporters on his website to a “major announcement” Tuesday evening regarding the 2014 GOP Kansas Senate campaign.

The 42-year-old Johnson County doctor is expected to say he’s moving ahead with a GOP primary challenge to Roberts, who’s seeking a fourth six-year term in the U.S. Senate. No Democrat has announced plans to run.

Wolf is a political novice who says on his website that “career politicians” have failed. He could highlight the division playing out nationally among tea party conservatives and others in the Republican Party.

Roberts’ executive campaign manager Leroy Towns says Wolf has shown little willingness to talk about real issues.