First-term Senate Republicans are jockeying for position and power in a Conference that could find itself in the majority 13 months from today.

Senators are ambitious by nature. But a burgeoning Republican caucus, a scarcity of available top committee and political positions and the lure of influencing the agenda in a GOP-controlled chamber could generate intense competition among a group of new Members who appear more impatient than those of past eras. This maneuvering, already under way, has been fueled partly by the unexpected choices of some veterans to step aside.

Twin decisions by Minority Whip Jon Kyl (Ariz.) to retire and by Conference Chairman Lamar Alexander (Tenn.) to relinquish his leadership post in January have sparked a scramble to advance, already drawing in Sen. Ron Johnson (Wis.) — and possibly fellow freshman Sen. Roy Blunt (Mo.) — in a race for Conference vice chairman. Sens. Rob Portman (Ohio) and Pat Toomey (Pa.) both serve on the Joint Committee on Deficit Reduction and have been showing assertiveness typically reserved for veterans.

Republican Conference Vice Chairman John Barrasso, a candidate for GOP Policy Committee chairman in the leadership elections set for January, has shown how a newcomer can move up quickly. The Wyoming Senator played a key role for the caucus in 2009 and 2010 as Republicans tried to block President Barack Obama’s health care law, moving into leadership last year when Sen. Lisa Murkowski (Alaska) relinquished her post.

“I just want to work together with others to help improve legislation and help improve the lives of people from around the country and people in my home state of Wyoming,” Barrasso, an orthopedic surgeon elected in 2008, said in an interview. “It was just the coincidence that the No. 1 topic on debate and on the minds of the American people at the time [I arrived] was an area where I had a lot of expertise.”

First-term Senators interviewed for this story, and their staffs, offered similarly generic platitudes about helping their colleagues, the country — and “luck” — when asked to discuss strategy for career advancement in a chamber notoriously populated with ambitious yet sensitive egos. These Republicans were hesitant to embrace the “rising star” label or concede to internal political maneuvering.

“The Senate’s got a lot of people on both sides of the aisle who are well-known — some famous people,” one Republican Senator said. “But my sense is, the folks who perhaps are more low-key and work as a team are more successful in getting things done.”

Only a few new Republicans entered the Senate in 2006 and 2008. But the Conference is now littered with up-and-comers following the 2010 midterm elections, which saw an infusion of several GOP Members with the potential to become major Senate players, national figures — or both. Another injection of new blood is possible in 2012, when Republicans will need to net four more seats to take control of the chamber.

First-term Republicans who have worked to move up or are viewed as on the rise include Sens. Kelly Ayotte (N.H.), Bob Corker (Tenn.), Mike Johanns (Neb.), Rand Paul (Ky.), Marco Rubio (Fla.), Blunt, Johnson, Portman and Toomey. Sen. Scott Brown entered the chamber with star power in the wake of his heralded 2010 special election victory in solidly Democratic Massachusetts, but he has sought a lower profile as his 2012 re-election bid gets under way.

Rubio was practically a national figure before he took office in January and is expected to be on the short list of potential Republican vice presidential candidates. He is also seen as a future White House candidate. In fact, among his advisers and staff are operatives with extensive presidential campaign experience. The Senator downplays talk that he might run for national office, saying he is focused on Florida.

But there is a distinct national flavor to the legislation and issues he has chosen to become involved in. Rubio focuses his agenda on foreign policy and national security issues, in addition to state matters. His most recent proposal is a United Nations reform bill. He also has spoken out on broad fiscal issues. Rubio said last week he decides where to be active based on what he cares about and where he can be effective.

Portman, also considered a possible GOP running mate in 2012, is another freshman who entered the Senate with an already-elevated profile. A former House Member as well as U.S. trade representative and budget director under President George W. Bush, Portman has recently been a leader in developing the GOP jobs agenda, played a key role in the passage of three free-trade agreements and is a super committee member. Portman declined to comment for this story.

But knowledgeable Republican operatives said the Ohioan’s strategy for exerting influence has been threefold: being proactive in seeking a position of leadership on an issue — and being willing to put in the hard work required to see it to conclusion; being inclusive, ensuring that any effort he is involved in is viewed as a Conference effort; and knowing when to shut up.

During private caucus meetings, when all Members are invited to advocate political and legislative strategy, Portman doesn’t always speak up. His method has been to be selective in choosing which issues to lead on, to invite wide participation and introduce the final work product as a Conference product, not the Portman plan.

Johanns, a former governor and Agriculture secretary, has sponsored a few major pieces of legislation, including a law repealing a tax-reporting requirement from the health care law.

The Senator, who considered running for Conference chairman in the 113th Congress until Alexander’s decision to step aside, said he got the idea to pull out of the race from talking to constituents during a town hall meeting. Johanns’ legislative efforts have repeatedly received national attention. But the Nebraskan said that was unintentional — that his agenda tends to reflect Nebraska’s needs.

“We go out, we listen to people, we sit down with our business community, our ag groups, our communities and start to hear what’s on their minds,” Johanns said. “It gives me the ability to focus.”