Ted Cruz bats for Oklahoma conservative
© Greg Nash

Sen. Ted CruzRafael (Ted) Edward CruzDebbie Wasserman Schultz marks 10 years as breast cancer survivor Foreign agent registration is no magical shield against Russian propaganda Let Trump be Trump and he'll sail through 2020 MORE (R-Texas) is going to bat for T.W. Shannon, saying the former state Speaker will be a conservative fighter for Oklahoma in the U.S. Senate.

It's a rare entry into GOP primaries this cycle for Cruz, who has only endorsed in two open-seat races — this one and Nebraska’s Senate race, where his preferred candidate, Ben Sasse, won the nomination. 

Shannon is battling Rep. James Lankford (R-Okla.) and a handful of other candidates in a GOP primary for retiring Sen. Tom Coburn's seat.

“In Oklahoma, there are a number of good Senate candidates, but T.W. Shannon is a conservative fighter,” Cruz says in the ad from the Senate Conservatives Fund.

“He has the courage to look Washington insiders in the eye, and say, ‘I don’t work for you, I work for the people of Oklahoma,’ ” Cruz adds.

The ad starts running Thursday and will air through the Tuesday primary. The group is spending $163,000 on the ads. 

Most polling has shown a tight race, with Lankford holding a varying lead. Shannon’s team has said he sees his most likely opportunity for success if the candidate can force a runoff with Lankford on Tuesday.