Barack Obama has made cracking down on K Street a signature cause of his presidency. But a year into his tenure, the executive branch’s revolving door has already started to turn with one senior official making the exodus from administration insider to hired gun.

Damon Munchus, the principal liaison between the Treasury Department and Congress regarding financial institutions and capital markets, signed on Monday as a managing director with financial services lobbying boutique the Cypress Group, whose clients include some of the nation’s biggest banks.

Munchus will be a test case for Obama’s tightened revolving-door policy, which prohibits former administration officials from lobbying the executive branch for the remainder of his administration. Munchus is the first example of an administration official leaving the Obama administration for a lobbying gig, according to several ethics lawyers, lobbyists and members of the government reform community.

While the former deputy assistant secretary for banking and finance under Treasury Secretary Timothy Geithner is barred from lobbying the Obama administration, he will register as a federal lobbyist, according to Cypress Group’s Ben Dupuy.

He faces no limits on immediately lobbying Congress.

“Damon signed the Obama administration ethics pledge and is committed to fulfilling it,” Dupuy said. “Damon’s lobbying is going to be Congressional.”

Despite the Obama administration’s lobbying ban, Munchus’ inside knowledge of how key decision-makers, such as Geithner, approach legislative issues will be a big lure for clients, according to K Streeters.

“He can still have a lot of impact,” said one financial services executive speaking on condition of anonymity. “It would be more effective if he could go right to the White House, but it’s not going to hurt him significantly.”

Munchus’ finance background at Treasury and his position as a member of Obama’s FDIC Review Transition Team — and, before that, as a financial analyst at Fannie Mae — will fit nicely with Cypress Group’s clientele, according to K Streeters.

The firm has a cadre of financial services industry clients, including Citigroup, Key Bank, the Managed Funds Association, the International Swaps and Derivatives Association, and US Bank, according to Senate lobbying records.

Munchus has not previously been a registered lobbyist.

GOP lobbyists say Munchus’ swift move from government official to K Street lobbyist is a sign that the revolving door is alive and well, despite Obama’s efforts to curb it.

“Where are the watchdogs? What does the lobbying czar say? What does Geithner and Obama think?” said one Republican lobbyist, speaking on background.

Ethics reformers agree that the revolving door needs to be closed, but they are looking for Congress to take action.

“This former executive officer will abide by Obama’s order, but there isn’t anything that Congress has implemented to restrict his lobbying Congress,” said Craig Holman of Public Citizen. “There is still a revolving door problem at the Congressional level.”

Still, Holman said he’s hopeful that Congress could expand a lobbying ban in legislation focused on the recent Supreme Court’s decision on campaign finance. So far, no formal legislation has been drafted.

Munchus’ arrival at Cypress Group comes on the heels of another addition to the firm, Republican Jeb Mason. Mason, former deputy assistant secretary for business affairs under then-Treasury Secretary Henry Paulson, was tasked with business outreach and coalition building in the Bush administration.

However, Mason will not register to lobby, according to Dupuy. He’ll be a member of the firm’s spinoff, Cypress Advisory Services, which is primarily focused on political intelligence gathering: helping clients understand regulatory policy and where legislative action is headed.

And Mason is opening the firm’s Dallas outpost, while Munchus will open a New York office for the firm.

“These are talented individuals who add a lot of value to our firm and we thought it was a great opportunity to bring them on board,” Dupuy said of the hires. “The fact that they both came from the Treasury Department — it’s not as if we set out six months ago to get a Paulson Treasury official and a Geithner Treasury official.”