When the Senate Conservatives Fund in 2012 made its first endorsement in a House race, supporting Rep. Jim Bridenstine, R-Okla., its motives were transparent.

The SCF, a major outside group best known for its sometimes disruptive role supporting conservative candidates in races for safely Republican seats, wasn't suddenly getting into the business of affecting House outcomes. It was grooming a candidate to one day win a seat in the Senate.

“We haven’t been shy about saying we would love to see Jim Bridenstine run for the U.S. Senate,” SCF Executive Director Matt Hoskins told the Washington Examiner last year.

Hoskins and the SCF had sights trained in particular on the seat held by Sen. Tom Coburn, another Oklahoma conservative, who has long planned to retire in 2016, at the end of his second term.

But SCF's plan could now be in flux, or at least accelerated, after Coburn announced Thursday that he will leave office early, at the end of this Congress, rather than fill out his term by serving through 2016. To fill the vacancy, Oklahoma Gov. Mary Fallin, a Republican, will call a special election.

Late Thursday, Hoskins was coy when asked whether Coburn's retirement would affect Bridenstine's plans — and, indeed, Hoskins did not mention Bridenstine at all.

"Dr. Coburn has been a tireless fighter against wasteful Washington spending," Hoskins said. "No senator has done more to research and expose our government's gross abuse of American taxpayers. This is a big loss for Oklahoma and the country."

Bridenstine's office was also mum on whether the lawmaker's sights are set on Coburn's seat.

"Rep. Bridenstine has indicated that he feels it is appropriate to focus on Dr. Coburn today," Bridenstine spokeswoman Sheryl Kaufman said, declining any campaign-related comment.

Two well-established Oklahoma lawmakers could pose a challenge to Bridenstine in a Republican primary, were they to enter the race: Reps. Tom Cole, a close ally of House Speaker John Boehner, and James Lankford, the No. 5 Republican in the House.

But Bridenstine's path to the House was as a dark-horse candidate, boosted by the SCF. He won his Republican primary race by besting Rep. John Sullivan, who had served five terms in Congress.