Each of the three men running to replace retiring Sen. Tom Coburn, R-Okla., refused to commit to supporting Senate Minority Leader Mitch McConnell to continue leading the Republican conference.

Former state Sen. Randy Brogdon has targeted the Kentucky senator most directly, opening his campaign with a statement saying that McConnell "has been complicit in growing the scope of government" and that he should "resign immediately."

Brogdon entered the race late and has the lowest profile of the three candidates, so it makes sense for him to punch up like that, but even state Rep. T.W. Shannon, who recently stepped down as House Speaker to focus on his U.S. Senate campaign and is one of the Republican National Committee's "rising stars," faults McConnell for failing to provide necessary "leadership."

"There is no question that we need new leadership in Washington D.C. from top to bottom," Shannon told the Washington Examiner, though he stopped short of promising to vote against McConnell in the next leadership race.

"I need to see who else is running," Shannon said. "I don't know who all the choices are. Between McConnell and Harry Reid, I think it's pretty clear, but I'd like to see who else is running. But we certainly need leadership. That's the problem in the country: we've got a lack of leadership."

U.S. Rep. James Lankford, R-Okla., who is regarded as the frontrunner in a horserace with Shannon, dismissed the whole line of questioning. "I know that makes good fodder at the beginning," he told the Examiner. "That's posturing as you walk through in a primary." But Lankford also said that he doesn't "know who is running" for leadership.

That reticence to support McConnell comes with him and the National Republican Senatorial Committee in a fight with Senate Conservatives Fund, a group founded by former Sen. Jim DeMint that has endorsed several candidates in Republican primaries -- including McConnell's challenger in Kentucky Matt Bevin, as well as Chris McDaniel, who is running against Sen. Thad Cochran, R-Miss.

“I think we are going to crush them everywhere,” McConnell told the New York Times in an interview published Sunday. "I don't think they are going to have a single nominee anywhere in the country."

McConnell's confidence notwithstanding, Shannon hopes to be on the wrong side of him in this primary race, telling the Examiner that he has reached out to SCF for their endorsement. Asked about the efficacy of outside groups spending money in Oklahoma, Shannon gave the kind of response you'd expect from a candidate hoping to get such a boost.

"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."

Still, it's not clear that this race will fall out along the lines drawn in other primaries. SCF wanted U.S. Rep. Jim Bridenstine to run for the seat, but he declined. The group hasn't signaled support for any alternative candidates.

The state's other GOP senator, Jim Inhofe, predicted the race would not turn into an insider-outsider battle. "I know Shannon well enough to know that it's not going to be that way," he told the Examiner during an interview outside the Senate chamber. "It's going to be tight between the two of them. I would say James Lankford and Shannon are both very good friends of mine, I'm not taking sides. But Lankford was first in line, so he I think started out with more resources than Shannon. Now Shannon is really aggressive right now ... so we've got ourselves a primary there."

He predicted that both Shannon and Lankford would support McConnell for Republican leader. "That doesn't sound like a position that they're taking," he said. "I mean, that's easy to say, 'well, let's just wait and see who is running.' "

In the meantime, Coburn said Oklahoma is different from some other states, where there is an advantage to be had in going after McConnell.

"I don't think that picks him up a single vote in Oklahoma," he replied when asked about Shannon's comments.