Rep. James Lankford (R-Okla.) announced Monday that he will run in the special election to fulfill the remainder of Sen. Tom Coburn's (R-Okla.) term.
In an interview with the Associated Press, Lankford said he hoped to represent "conservative solutions that most Americans believe in."
"We're facing serious issues," Lankford told the AP. "We can either complain about it or try to step in and solve it."
Coburn, who was diagnosed with prostate cancer last fall, announced last week he intends to retire at the end of this congressional session. Coburn, first elected in 2004, was reelected for a second term in 2010. The special election's victor will serve out the remaining two years of his term.
The Senate Conservatives Fund, a group backing conservative challengers in Senate races, was quick to strike against Lankford's candidacy.
"We won't support Congressman Lankford's bid for the Senate because of his past votes to increase the debt limit, raise taxes, and fund Obamacare," Matt Hoskins, the group's executive director, said in a statement. "We have reviewed his record and it's clear that conservatives cannot count on him to fight for their principles."
Instead, the group said it would like Rep. Jim Bridenstine (R-Okla.), a tea party favorite, to jump in the race.
Rep. Tom Cole (R-Okla.), eyed as another potential challenger, said Sunday he would not run for the seat.
A primary election for the seat will take place on June 24. A potential runoff would be on August 26, and the general election is on November 4.