Former Oklahoma House Speaker T.W. Shannon received the endorsement of the Senate Conservatives Fund, raising the likelihood that his campaign with Rep. James Lankford, R-Okla., to replace retiring Sen. Tom Coburn will turn into a new battleground between Republican leadership and outside conservative groups.

"T.W. Shannon believes in the principles of freedom that make this country great and will stand up to the big spenders in both parties to balance the budget and stop Obamacare," SCF executive director Matt Hoskins said. "We're supporting T.W. Shannon because he's a principled conservative, he has strong grassroots support in Oklahoma, and he can win if Americans come together to support his campaign."

That endorsement could make Shannon an enemy of Senate Minority Leader Mitch McConnell, R-Ky., who wants to "crush" SCF in every race where they have endorsed a candidate.

"I don't think they are going to have a single nominee anywhere in the country," McConnell told the New York Times.

Shannon told the Washington Examiner at CPAC that he hoped to get the SCF endorsement, adding that independent expenditures by outside groups can be effective in his state.

"Oklahoma voters are savvy enough to know what the truth is about candidates," he said. "I think they're very savvy about vetting candidates and so, where the message is coming from, if it's an accurate message, I think they'll listen to it, I think they know."

Rep. Jim Bridenstine, R-Okla., who declined to run for the Senate seat, was SCF's top choice, so it wasn't clear that they would get involved in this race.

Sen. Jim Inhofe, R-Okla., predicted that the campaign would not turn into the kind of insider-outsider battle that has unfolded in other races, such as Chris McDaniel's bid to unseat Sen. Thad Cochran, R-Miss.

"I know Shannon well enough to know that it's not going to be that way," he told the Examiner.

Sarah Palin framed the race in exactly those terms when she decided to endorse Shannon. "T.W.'s opponent has the backing of Beltway insiders, but T.W. has the passion and experience we the people need in Washington," she said.