After three decades on and around Capitol Hill, star politician Fred Thompson (R) can call on a tight knit, but low-key squad of loyalists.

The operatives, now mostly ensconced in senior K Street posts, have been batting away appeals from rival camps while the former Tennessee Senator contemplates a jump from the small screen to the national stage for a GOP presidential run.

If he enters the race, those close to Thompson said, the group would help make up a brain trust for his still-unformed campaign organization.

“I’ve been getting calls from people who know I know him, saying ‘If he decides, make sure he knows I want to participate,’” said Tim Locke, a lobbyist at the Smith-Free Group and former aide to ex-Sen. Howard Baker (R-Tenn.). “The excitement of his potential candidacy is extraordinary,” said Locke, who befriended Thompson 30 years ago.

In addition to Locke, the group includes A.B. Culvahouse, who chairs O’Melveny & Myers, a sprawling international law firm; Ken Rietz, a Republican strategist and top public relations executive; Mike Madigan, a partner with Akin Gump Strauss Hauer & Feld; and Tom Daffron, chief operating officer of the Jefferson Consulting Group, a local lobbying outfit.

Among them, only Locke and Culvahouse have Tennessee roots. Locke was born in tiny Mount Pleasant, Tenn., about a half-hour drive from Thompson’s hometown of Lawrenceburg, Tenn.

Madigan worked alongside Culvahouse and Thompson when all three were aides to Baker in the 1970s during the Senate investigation into the Watergate scandal. And most of them pitched in when Thompson ran for an open Senate seat in 1994. Thompson won, and Daffron joined his office as chief of staff.

Most of the five also have had careers at the highest levels of government. Daffron, for example, has served as a top aide to two other Senators, and got exposure to presidential campaigns as national campaign manager for the 1999 White House run of now-Sen. Elizabeth Dole (R-N.C.).

Madigan, a top white-collar criminal lawyer, took a break from his practice in 1997 to serve as Thompson’s chief counsel for his campaign finance investigations before the Senate Governmental Affairs Committee.

Rietz, in addition to stints on both sides of the Capitol, served as a top executive at Burson-Marsteller, at one time chairing the firm’s global public affairs practice.

For now, those close to the former Senator said any role they would like to play in a presidential campaign has been limited by Thompson’s careful avoidance of a traditional candidacy. He has no national political or fundraising apparatus in place, and apparently has made no moves toward constructing one.

That compares with the three leading contenders for the GOP nomination, who have amassed small armies of supporters in the lobbying world, a key source of fundraising muscle and political know-how.

Still, Thompson is running second or third in most national polls, and his would-be K Street backers said they are fielding calls from operatives disillusioned with the current field and eager to work for him. “It’s potential vendors, staffers, subject experts,” one Thompson associate said.

The names get forwarded along to Bobbie Murphy, a Tennessean who first started to work for Thompson when he was in private legal practice in Nashville, Tenn. Sources said Rietz also has been tasked with keeping up with potential supporters.

Mark Corallo, a former Justice Department official who is volunteering as Thompson’s spokesman, said, “In any political venture, the first people you start with are your friends. Then you widen the circle.”

Meanwhile, Thompson largely has relied on public surrogates to make the case for, and to, him. Volunteer State Republicans — including former Sens. Baker and Bill Frist, Sen. Lamar Alexander, and Reps. Zach Wamp and John Duncan — have been out front beating the drum. Wamp and Duncan are operating a 527 political group in Tennessee to build support for a Thompson candidacy. Frist has largely turned over his Web site to promoting his old colleague.

The former Senate Majority Leader had assembled the beginnings of a campaign team for his own White House bid before deciding last year he wouldn’t make the race. Frist’s inner circle also is expected to pitch in to a Thompson organization if he joins the race.

Beyond a top echelon of longtime aides and Tennessee powerbrokers, Thompson also can call on a broader roster of former staffers, many of whom have set up shop in the lobbying world.

Thompson turned up to greet about 40 of them in late March when they gathered for a semiannual reunion at Charlie Palmer Steak on Capitol Hill. Chris Lamond, who organized the event, started as Thompson’s driver in 1994 before moving up to handle policy.

“Of course we would love for him to get in the race,” said Lamond, now a lobbyist with Ogilvy Government Relations. And while the reunion was unrelated to Thompson’s potential candidacy, it clearly created a spike in attendance.