Rep. James Lankford (R-Okla.) announced Monday that he will seek the seat being vacated by retiring Sen. Tom Coburn (R-Okla.).
"After a great deal of thought, prayer and discussion with my family, I feel led to continue my Oklahoma common sense and principled approach to attack the deep problems in the United States Senate," Lankford said in a statement.
Lankford, 45, has served in Congress since winning his seat in the 2010 election. The former youth camp director has quickly risen to become chairman of the House Republican Policy Committee.
He is the first major candidate to enter the race. Other potential candidates include Rep. Jim Bridenstine (R-Okla.) and state House Speaker T.W. Shannon (R).
Coburn will resign his seat at the end of the current Congress, and the final two years of his current term will be at stake in a special election held on Election Day. Holding the race on Election Day means elected officials must forfeit their current seats to run for Coburn's.
Rep. Tom Cole (R-Okla.) and state Attorney General Scott Pruitt (R) both announced Sunday that they wouldn't run.
Republicans are expected to retain the seat in deep red Oklahoma.
There has been some speculation that Coburn might endorse Lankford, but a Coburn spokesman on Monday downplayed that possibility.
"It isn't likely Dr. Coburn will formally endorse anyone but may support a candidate in his capacity as a citizen," Coburn spokesman John Hart said.
Lankford also won't be getting the backing of key conservative groups, who were quick to announce their opposition to him. Among the groups who want an alternative to Lankford in the primary are the Senate Conservatives Fund and the Club for Growth.
"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," SCF executive director Matt Hoskins. "We have reviewed his record and it's clear that conservatives cannot count on him to fight for their principles."
Updated at 4:33 p.m.