In the latest illustration of the shift, South Dakota Sen. John Thune, the No. 2 Senate Republican, is set to endorse Walker on Monday. In a statement to POLITICO, Thune called Walker “a fighter, a uniter, and a proven winner.”

Thune is the first member of Senate GOP leadership to endorse Walker, and his support is the newest evidence the former football star has tacitly won the party hierarchy’s blessing. While Minority Leader Mitch McConnell has yet to give the Hall of Famer his explicit backing, the Kentucky Republican told POLITICO last month that “there’s every indication he’s going to be a good candidate.”

Walker’s newfound support could go a long way toward helping him lock up the Republican nomination. He has already received the backing of Trump, a longtime Walker friend who recruited him into the race. Trump appeared with Walker at a rally last month in Perry, Ga., where the former president invited him onstage to speak…

Walker has been waging a quiet effort to woo Senate Republicans and has spoken to Thune, among others. He has also talked with McConnell and Florida Sen. Rick Scott, the chair of the National Republican Senatorial Committee. The committee is remaining officially neutral in the primary, where Walker faces several lesser-known Republican opponents.