Sen. John Thune (R-S.D.) has officially jumped in the race for the No. 5 slot in the Republican leadership lineup, announcing he will run for Conference vice chairman.

Thune spokesman Kyle Downey confirmed that his boss has publicly declared his candidacy position, now held by Sen. John Cornyn (Texas). Cornyn is running for chairman of the National Republican Senatorial Committee, a post now held by Sen. John Ensign (Nev.) who is running to be the next Republican Policy chairman.

“Sen. Thune is running for Republican Conference vice chair. He has been talking with his colleagues to gauge their support and has been encouraged by what he is hearing,” Downey said.

Sens. Jeff Sessions (Ala.), Richard Burr (N.C.) and Lisa Murkowski (Alaska) also have all been mentioned along with Thune as possible candidates for the Conference vice chairman spot.