It’s finally less talk and more action from Fred Thompson in Washington.

While the former Tennessee Senator is sticking to his “testing the waters” mantra on a possible presidential bid, his supporters aren’t waiting around, setting up his first area fundraiser for next Monday.

Although the invitations went in the mail on Wednesday, Thompson allies have been working for weeks to secure the official host committee that includes a high-powered group of 35 business lobbyists and professionals, providing the first glimpse into Thompson’s ever-expanding base within the influence community and on Capitol Hill.

So far, Thompson is still relying largely on his home-state appeal, securing the support of former staffers and lobbyists with longtime Tennessee connections. But event organizers hope to expand beyond that base with the $1,000-per-person, $5,000-per-political-action-committee inaugural fundraiser at the JW Marriott. The 6 p.m. event will give many inside the Beltway their first chance to see Thompson — as the potential presidential candidate — in action.

“I think there’s a growing number of leaners for a Fred candidacy for whatever reason, the recent setbacks by Sen. John McCain, or it might just be a realization that the testing the waters committee will soon become the real deal, hopefully,” says Tim Locke, a lobbyist at the Smith-Free Group who is a Tennessee native and active Thompson supporter.

Thompson’s K Street backers represent some of the largest Fortune 500 companies and industries, ranging from health care and defense, to Wall Street and high-tech.

The three dozen or so members of the host committee include lobbyists like Sen. Dick Lugar’s (R-Ind.) son, David Lugar of Quinn Gillespie & Associates, Stephanie Henning of Pfizer, and Tom Collamore, a former in-house lobbyist at Altria Group who is now the Thompson campaign’s chief operating officer.

Chris Lamond of Ogilvy Government Affairs has been largely orchestrating Thompson’s downtown outreach efforts for the fundraiser.

Lamond, a former Thompson staffer, has enlisted a cadre of former Thompson aides-turned-lobbyists including Rachel Jones Hensler, now at the Nickles Group; David Schwarz of McKenna Long & Aldridge, and Paul Noe, vice president of regulatory affairs at the Grocery Manufacturers of America.

The event has also drawn support from Thompson’s former K Street colleagues, veterans like Bill Timmons Sr., a founder of Timmons & Co., lobbyist Rick Hohlt, a former Lugar aide in the late 1970s, and Patrick O’Donnell of Squire Sanders.

“I was ruminating on what I was going to do as I looked at the field,” says O’Donnell, who signed on to help raise money a few weeks ago. O’Donnell, who worked with Thompson in the 1980s at O’Connor & Hannan, says he is hoping to raise $25,000 for the event.

Although committee members say there is no official fundraising benchmark to meet to be on the host committee, each is trying to draw at least 15 to 25 people to the event that is expected to raise more than $250,000. And the number of people interested in attending has exceeded expectations, according to Hensler.

“These fundraisers typically start with the people that you know, the people you trust, perhaps people that once worked together —that’s the low-hanging fruit,” says Lugar, of Quinn Gillespie & Associates, who is one of the few committee members without direct ties to Thompson.

“What will happen here is as money starts to come in, the circle will expand as everybody senses the excitement that continues to build,” Lugar said.

That buzz has translated into more endorsements on Capitol Hill. Although Thompson hasn’t personally been back to the Hill since an April meeting he had with about 60 Members of Congress, he’s secured 18 current GOP lawmakers to be honorary host committee members for the event, including Tennessee Sens. Lamar Alexander and Bob Corker and Reps. Louie Gohmert (Texas), Don Manzullo (Ill.) and Roger Wicker (Miss.).

Thompson also has landed the backing of two of his former colleagues who are now downtown: Livingston Group founder and former Rep. Bob Livingston (La.) and former Tennessee Rep. Van Hilleary, who now lobbies at Sonnenschein Nath & Rosenthal.

And they aren’t finished trying to gin up support. Rep. Zach Wamp (R-Tenn.), who is leading the charge for Thompson in the House, says that he expects as many as 15 more House Members to endorse by the time of the July 30 fundraiser.

Should Thompson officially enter the race, he’ll be counting on his lobbyist contingency to help build up his fundraising numbers to compete against former New York Mayor Rudy Giuliani and former Massachusetts Gov.Mitt Romney in the GOP presidential primary. But his K Street supporters aren’t worried.

“I like the way Fred’s going about it,” says John Dowd, a lawyer at Akin Gump Strauss Hauer & Feld who recently switched his allegiance from McCain. “It’s more economical. It’s probably saved us $50 million.”

O’Donnell agrees. “I think he can raise the money that he needs to raise. He’s been having some fundraisers. … I think once he announces, I think he’s going to be able to pull together the support.”