Conservative outside groups are increasingly likely to stay on the sidelines in the Oklahoma Senate special election now that Rep. Jim Bridenstine has decided not to run, multiple GOP sources said.  

Groups like the Senate Conservatives Fund and the Madison Project had encouraged Bridenstine to run in the GOP primary as a conservative alternative to Rep. James Lankford, who was the first candidate to announce a bid . The entrance Wednesday by state Speaker T.W. Shannon, an African American named a rising star by the Republican National Committee, was met with equally little excitement among the groups.  

Unless another candidate is recruited, these groups may choose to sit out the race to replace resigning GOP Sen. Tom Coburn —  a hero among the conservative grass roots for his battles against government waste.  

“For the outside groups to back T.W., it means they really, really hate Lankford enough that they would back an RNC-touted candidate instead of sitting the race out,” said one Republican insider in Oklahoma.  

Reached on Wednesday, SCF Executive Director Matt Hoskins declined to comment when asked whether his group still intended to be involved in the race. A Madison Project spokeswoman did not return a request for comment.  

Club for Growth spokesman Barney Keller declined to comment on whether the club is considering backing Shannon. “We’re watching the race,” Keller said.  

Whether or not these ideological groups with a history of spending big in Republican primaries play here, the race to fill the remaining two years of Coburn’s term is already set up as a competitive affair between Lankford and Shannon.  

Shannon, a state legislator with ties to a national donor base, is a member of the Chickasaw Nation, giving him access to another fundraising avenue. Lankford, chairman of the House Republican Policy Committee, likely starts off the race with at least $455,000 in cash on hand, which he had at the end of September. He also has a sizable base of support among Christian grass roots that helped him in his first election to Congress in the 5th district.  

Bridenstine’s decision not to run also makes it more likely that the nomination will be decided in the June 24 primary . A field with three major candidates would have increased the chances of no candidate receiving at least 50 percent of the vote. In that event, a runoff would be held on Aug. 26.  

The GOP nominee will be heavily favored to win the special in November in this heavily Republican state. The race is rated Safe Republican by Rothenberg Political Report/Roll Call.