Republican Senators remain hesitant to publicly wade into the GOP presidential primary, although some Members are less shy than others in revealing whom they intend to support in a candidate field only beginning to take shape.

Sen. John Barrasso (Wyo.) is enthusiastically backing Sen. John Thune (S.D.); Sen. Orrin Hatch (Utah) is solidly behind former Massachusetts Gov. Mitt Romney despite the fact that Ambassador to China and former Utah Gov. Jon Huntsman Jr. might run; and Sen. Dan Coats (Ind.) hopes he will have the opportunity to endorse Indiana Gov. Mitch Daniels.

Planning to remain neutral in the primary is freshman Sen. Marco Rubio, a rising star from a key battleground state. In 2008, the Florida Republican endorsed former Arkansas Gov. Mike Huckabee. Sen. John Cornyn (Texas) will stay out the nominating process because of his position as National Republican Senatorial Committee chairman. Sen. Roy Blunt has relationships with many potential candidates and conceded that he has discussed the matter with some, but the Missourian said he is withholding any endorsement for now. Blunt backed Sen. John McCain (R-Ariz.) in 2008.

“I’ve talked to several of the candidates, and most of them I’ve known for a long time and I consider personal friends, and I’m going to keep talking to them,” Blunt said.

Around two dozen Republicans are now mentioned as potential candidates to seek the 2012 nomination to face President Barack Obama, but none of the most serious contenders have announced their candidacies. The spring of this year appears to be the target launch period for many of the candidates.

The list of unannounced candidates includes those who have supporters-in-waiting in the Senate, including Daniels, Romney — who also ran in 2008 — and Thune, who expects to make a decision by month’s end.

But announced or not, likely candidates are already in the process of staffing their Congressional relations teams.

“Everyone is putting someone in to do Congressional relations,” a Washington, D.C.-based Republican operative said. “Romney has his team and is actively recruiting Members.”

Even as Washington has gone out of fashion with American voters — particularly conservative Republicans who participate in primaries — GOP operatives say Members’ support is still coveted for access to contacts, campaign donors and political infrastructure within respective states. Blunt said those factors are what make Member endorsements valuable, as opposed to the image of having the personal, public backing of any particular Congressman or Senator.

However, another Washington-based GOP strategist said it is possible that the support of tea-party-backed freshman Members could be sought out over the next 18 months as Republican presidential candidates seek to trump each others’ conservative bona fides in a primary likely to be decided by such voters. This strategist said that these Members are not viewed as “part of the problem” that has led to unhappiness with Washington.

The lack of either a decision to run, or the announcement of an expected candidacy, on the part of the 2012 contenders has not dimmed the hope or enthusiasm of their supporters.

“I like John Thune a lot. He’s part of our Western Caucus; he knows the issues from my part of the country. He and I think a lot alike on issues; I talk to him frequently, I think he’d be a great president,” Barrasso said.

Barrasso, the Republican Conference vice chairman and No. 4 Senate Republican, serves in leadership with Thune, who as GOP Policy Committee chairman is the fifth-ranking Republican in the chamber.

Hatch said Huntsman’s potential entry into the race would not affect his support for Romney, a fellow Mormon who is also revered in Utah for his stewardship of the 2002 Winter Olympics in Salt Lake City. Huntsman has submitted his resignation as ambassador to China to the Obama administration, and he told the White House he plans to leave the post by May.

“I’ve been a big supporter of Romney,” said Hatch, who is preparing for the possibility of a tough intraparty challenge of his own in 2012. Hatch referred to Huntsman as “a very good friend and a very good person,” but said: “I had already committed to Mitt Romney and I’m not going to change that commitment.”

Hatch confirmed that, if asked, he would lend a hand to Romney’s campaign.

Coats, who won back his old Senate seat last year after retiring in 1998, said he has talked to Daniels about the possibility of running for president.

“I’m hoping my man Mitch is our candidate. But I’m waiting to see what his decision is before I make any other decision,” Coats said, referring to the slogan Daniels used in his two successful gubernatorial campaigns. “We have talked on a number of occasions, but he clearly has not decided what he’s going to do.”

Meanwhile, Rubio spokesman Alex Burgos made clear that Florida’s junior Senator would not endorse.

Rubio is a tea party favorite who also has demonstrated broad appeal within the GOP and across party lines. He is mentioned as being in the vice presidential mix in 2012. But Rubio has pursued a low profile since being sworn in, choosing to focus on the Sunshine State over anything that involves national politics. That includes turning down an invitation to speak at the Conservative Political Action Conference this week.

“In this race, he’s staying out of it completely,” Burgos said. “For the time being, politics is a distant second to the official business he has to work on.”