The potential for a high-profile Democratic squabble to succeed South Dakota Sen. Tim Johnson — who is widely expected to retire — has grabbed the spotlight of the race so far.

But the possibility of an equally contentious Republican primary is brewing beneath the surface.

For now, the Republican field remains a party of one. Former Gov. Mike Rounds, who jumped into the race in November, is viewed by Republican leaders from Washington, D.C., to Sioux Falls, S.D., as a top-tier recruit. If nominated, Republicans believe Rounds would put the party in a strong position to win one of the GOP’s best pickup opportunities.

However, Rounds is highly unlikely to have a free ride to the nomination, local GOP sources said. South Dakota conservative activists are desperately seeking an alternative to Rounds, a moderate whose eight-year tenure enraged many in the right wing of the party.

While they await a decision from Rep. Kristi Noem, who would offer Rounds a stiff challenge in the primary, one other potential candidate is state Senate Majority Whip Larry Rhoden.

“I think that it’s safe to say that there are a number of people in the state that would like a choice in addition to former Gov. Rounds,” Rhoden said in an phone interview. “I have had some conversations with many folks along that line. I certainly haven’t made any decisions but haven’t ruled it out at the same token.”

Rhoden added that any potential challenger to Rounds will have to weigh the former governor’s fundraising head start as part of the decision.

Rounds is well-connected and expected to excel at fundraising. He’s scheduled to attend a meet and greet near the White House next week hosted by former Mississippi GOP Gov. Haley Barbour.

Rounds certainly puts the seat in play for Republicans, but Noem is the candidate that conservatives want. That option remains on the table, a source close to Noem said, but she is unlikely to make a final decision any time soon — meaning a potential Rounds-Noem duel could hover over the race for the foreseeable future.

“She is still considering a run for Senate,” the source said, “but right now she thinks it’s too early, people are sick of politics and she’s focused on doing the best job she can for South Dakota.”

Some South Dakota Republican insiders believe Noem will ultimately take a pass, but even if she does, there are several others believed to be taking a look at the race.

Conservative former state Sen. Bill Napoli said that if Noem doesn’t run, he would consider filing paperwork to establish an exploratory committee and asking for financial pledges — which he did in a brief 2006 gubernatorial bid.

Still, there is not an organized conservative grass-roots effort yet, GOP sources said, and conservative outside groups have not yet homed in on the race. The absence of funding and organization would make mounting a competitive bid an even steeper climb without Noem.

Conservatives are concerned that Rounds will once again slide into statewide elected office. He benefited in 2002 from a bitter three-way gubernatorial primary, when the two better-financed candidates focused their attacks on each other and ultimately allowed Rounds to differentiate himself as the more positive of the three.

Former state Sen. Gordon Howie, who runs a conservative organization called the Life and Liberty Group, said he has so far been unsuccessful in recruiting a candidate to run. But he said he’s doing everything he can to encourage Noem.

“We just don’t believe his record is conservative,” Howie said of Rounds. “He’s a nice man. I would have coffee with him. But I won’t vote for him.”

Meanwhile, the Democratic primary could feature an epic contest between the state party’s two most powerful brands. U.S. Attorney Brendan Johnson, who is Tim Johnson’s son, and former Rep. Stephanie Herseth Sandlin, who lost to Noem by 2 points in 2010, are both believed to be seriously considering running — even though the elder Johnson has not yet formally announced his plans for 2014.

Democrats have a strong recent track record when it comes to avoiding crippling primaries, and the party hopes to avoid what would likely be an expensive nominating fight.

This is one of the party’s most vulnerable seats, with or without Johnson running for re-election. On the other hand, the GOP’s hopes of taking the Senate majority rely on picking up this vital and vulnerable seat.

But thanks to the influence of outside issue-based groups, Republicans in recent cycles have been less successful navigating primaries, the result of which has facilitated the loss of several winnable seats and left the party six seats from the majority.

“Mike had pretty strong approval ratings all through his eight years, and I think taking him on for any other Republican would be difficult,” South Dakota GOP Chairman Craig Lawrence said. “But we certainly welcome them to join in the fray if that’s what they want.”