Hartford — Embattled House Speaker Christopher Donovan, D-Meriden, will temporarily relinquish his leadership role during the state legislature's forthcoming special session and has hired former U.S. Attorney Stanley Twardy Jr. to investigate all contributions to his campaign for Congress.

The announcement Friday afternoon came from Donovan's new campaign manager, Tom Swan, who was hired in the wake of an undercover FBI investigation and arrest Thursday by federal authorities of the campaign's finance director.

Robert Braddock Jr., 33, of Meriden was charged with concealing campaign contributions. Authorities say Braddock attempted to obscure the source of as much as $20,000 in contributions to Donovan's campaign for the 5th Congressional District.

According to the criminal complaint, the individuals who were actually behind the contributions had an interest in seeing the defeat of legislation this spring that would have subjected some roll-your-own smoke shop owners to new licensing fees and a tax increase.

The bill died without coming to a vote in either of the two General Assembly chambers.

Donovan is the state Democratic Party's endorsed candidate to replace U.S. Rep. Chris Murphy, who is running for U.S. Senate. He faces an Aug. 14 primary.

At a news conference outside the Capitol, Swan insisted Donovan was unaware of the alleged improprieties and "did nothing wrong." He pointed out how the lawmaker acted swiftly in firing Braddock and two other campaign workers as soon as the allegations surfaced.

"He goes between feeling sick and disappointed and angry," Swan said. "He wants to make sure we get to the bottom of whatever went wrong, that it gets corrected and that we move forward."

Swan told reporters that as far as he knew, Donovan was not a target in the ongoing FBI probe and continued to cooperate with authorities. The lawmaker hired an attorney this week upon learning of the investigation.

Swan is executive director of the Connecticut Citizen Action Group, a progressive consumer and political group, and ran Ned Lamont's 2006 campaign against U.S. Sen. Joe Lieberman. He said he has known Donovan for 18 years and recalled having an intimate conversation with him before agreeing to join the campaign.

"I looked him right in the eye and I said, 'Is there any truth to this, and did you do anything wrong?'" Swan said. "And he looked me in the eye, and he said, 'No.'"

Donovan will remain House speaker, Swan said, but will recuse himself from drafting or negotiating legislation during the June 12 special session. The session is to deal with various budget implementation bills left over from this spring's regular session, and possibly a bipartisan bill aimed at creating jobs.

Donovan wants House Majority Leader Brendan Sharkey, D-Hamden, to take over his leadership duties that day "in order to remain above even the appearance of impropriety," Swan said.

Earlier in the day, the minority leader of the state Senate called for Donovan to immediately give up the speakership.

"The facts and allegations in the affidavit are a grave violation of the public trust and cast a pall on all of the legislative activities Speaker Donovan has participated in since announcing his run for Congress," said Sen. John McKinney, R-Fairfield.

In a joint statement, the Senate's Democratic leaders said Donovan's decision to step aside at the rump session later this month was a good one.

"The allegations regarding concealed contributions, however, are serious and disturbing," said Senate President Pro Tempore Donald Williams of Brooklyn and Majority Leader Martin Looney of New Haven. "We urge the Speaker to immediately, directly and personally answer all questions related to these allegations."

Donovan was not present Friday to answer questions from reporters; Swan said he advised him to stay home. "Chris wants to figure out more information like all of us do about what happened and to be able to determine what are the appropriate next steps," Swan said.

Gov. Dannel P. Malloy has called the federal allegations "despicable" and urged Donovan to give a full public explanation. "Allegations like (these) not only damage a campaign or a candidate, they also undermine citizens' belief in their government's ability to carry out its responsibilities," the governor said.

Donovan's campaign hired Twardy to examine all contributions to date. Disclosure filings through April 24 show the campaign had raised more than $1 million.

Twardy was U.S. Attorney for Connecticut from 1985 to 1991 and then left to become chief of staff for former Gov. Lowell P. Weicker Jr. Earlier this spring he was named a managing partner at the Day Pitney law firm.

Twardy is to start examining contributions today. The task is expected to take 15 days.

"Whatever we find, we will turn over to the U.S. attorney," Swan said, and any "ill-gotten" contributions will be donated to the state's Citizens' Election Program.

Donovan was a strong proponent of the program, which provides public financing for individuals running for a state office.

"He along with Don Williams and Jodi Rell are the reason that Connecticut has the best public financing system in the entire country," Swan said. "They wanted to make sure elections were about democracy and not who could raise the most money."

j.reindl@theday.com