Lankford said Monday that reducing the nation's deficit and long-term debt and pushing for states' rights will continue to be among his top priorities in office.
"Conservatives have increasingly grown more and more frustrated and caustic when we should grow more committed and more focused," Lankford said to a group of supporters during a press conference at the Oklahoma History Center. "The problems we face today and the gridlock in Congress will be solved with a clear set of conservative solutions, a commitment to do the work, and a Senate transformation."
A longtime director of one of the nation's largest Christian youth summer camps, Lankford was a political unknown when he emerged from a crowded Republican primary field in 2010 to win the U.S. House seat. He won re-election in 2012 and was the only member of Oklahoma's House delegation to not face a GOP primary opponent that year.
Lankford also has risen quickly among the GOP leadership in the House, and is currently the chairman of the Republican Policy Committee. He also landed a spot on the House budget committee.
But he also drew criticism from the Virginia-based Senate Conservatives Fund, which said in a statement Monday that it would not support Lankford in a GOP primary because of his votes on increases to the debt limit and a recent bipartisan budget bill.
"We have reviewed his record and it's clear that conservatives cannot count on him to fight for their principles," the group's executive director, Matt Hoskins, said in a statement.
The decision by Coburn, who is battling a recurrence of cancer, to resign the seat two years early has turned a somewhat predictable election year in Oklahoma on its head. The special election will coincide with the regular election cycle in 2014, meaning there will be two U.S. Senate seats on the ballot in Oklahoma as U.S. Sen. Jim Inhofe seeks re-election.
"A week ago we were talking about a concern for voter intensity. I think this takes care of that," said Dave Weston, chairman of the Oklahoma Republican Party.
It's the first time since 2004 that Oklahoma has had an open Senate seat, and Republicans will be heavily favored to maintain it. Oklahoma has not elected a Democrat to the U.S. Senate since David Boren in 1978. Among Democrats expected to consider the race are former Gov. Brad Henry and former Attorney General Drew Edmondson. Telephone messages left Monday for Henry and Edmondson were not immediately returned.
Other Republicans considering running for the open Senate seat are U.S. Rep. Jim Bridenstine of Tulsa and state House Speaker T.W. Shannon of Lawton.
"No one can replace Tom Coburn, but someone will succeed him," Shannon said in a statement Monday. "I am praying with my family about whether to enter the race to do just that, and I know the Lord will clearly place on my heart what my assignment is."
Bridenstine spokeswoman Sheryl Kaufman said the first-term congressman is considering a run, "but he's not inclined to make a rushed decision."
Lankford has the advantage of a hefty campaign account. He reported having more than $450,000 in cash on hand at the end of September, the most recent report available, and that money can be used for a Senate campaign. Bridenstine reported having about $180,000 in cash at the end of September.
Lankford declined to say how much he currently has raised, but the next campaign finance report is due next week.
On Sunday, Attorney General Scott Pruitt and U.S. Rep. Tom Cole, R-Okla., both said they would not run for Coburn's seat. Gov. Mary Fallin also has said she won't run for the seat.
The timing of the special election means most officeholders who run for the seat, including Lankford, will not be able to run for re-election to their current positions. His announcement is expected to trigger another wave of candidates seeking to replace him in the 5th District. Former state Rep. Shane Jett already has said he plans to run. Other Republicans considering the race for Lankford's seat include Corporation Commissioner Patrice Douglas; state Sens. Clark Jolley, Greg Treat and David Holt; former state Sen. Steve Russell; and state Rep. Paul Wesselhoft.
Lankford said Monday he has no plans to endorse a candidate in the primary race for his open seat.
"I'll stay out of it," he said.
On the Democratic side, retired University of Central Oklahoma professor Tom Guild, who ran unsuccessfully for the post in 2010 and 2012, already has announced his plans to run again for the 5th District in 2014, and former Corporation Commissioner Jim Roth said he's considering the race.
Sean Murphy can be reached at www.twitter.com/apseanmurphy.