FILE - In this March 14, 2016 file photo, Massachusetts Senate President Stanley Rosenberg speaks during a signing ceremony for legislation aimed at reversing a deadly opioid addiction crisis at the Statehouse in Boston. Rosenberg on Monday, Dec. 4, 2017, agreed to relinquish his responsibilities as Senate leader during an investigation into sexual misconduct allegations involving his husband (AP Photo/Elise Amendola, File)

BOSTON - The president of Massachusetts' state Senate changed course Monday and agreed to relinquish his leadership responsibilities during an investigation into sexual misconduct allegations involving his husband.

President Stan Rosenberg, a Democrat, had originally said he would recuse himself only from any matters related to the investigation or the allegations against Bryon Hefner.

Rosenberg informed senators just prior to a closed-door Democratic caucus that he would step aside temporarily, though he would remain in the Senate.

"I believe taking a leave of absence from the Senate Presidency during the investigation is in the best interest of the Senate," Rosenberg said in a statement. "I want to ensure that the investigation is fully independent and credible, and that anyone who wishes to come forward will feel confident that there will be no retaliation."

Rosenberg, who has not been accused of wrongdoing, expressed shock over the allegations reported last week by The Boston Globe. The Democrat maintained that his husband had no influence over his policy decisions or actions by the Senate.

Several men told the Globe that Hefner sexually assaulted or harassed them, including three men who said Hefner grabbed their genitals. The men, who were not named by the Globe, said they did not report the alleged incidents partly because they did not want to alienate the powerful Senate leader.

Attorney General Maura Healey and Suffolk County District Attorney Daniel Conley, both Democrats, said Monday they are prepared to launch an investigation and said anyone with information should feel free to contact either of their offices.

The two said in a written statement Monday that they are committed to providing every survivor of sexual assault "a safe, respectful, victim-centred environment."

Most Democratic senators were grim-faced and refused comment as they entered the caucus, which ran well into the afternoon, with reporters staked outside the room.

Senate Majority Leader Harriette Chandler, the No. 2 Democrat in the Senate, emerged briefly in the late afternoon to tell reporters that a "very intense and very open" discussion was taking place behind closed doors but she did not divulge details.

Lawmakers were expected to vote later Monday on a plan to appoint an independent investigator whose focus likely would be on whether Rosenberg knew about Hefner's alleged behaviour, or if Hefner had any clout when it came to matters before the chamber.

Only one senator, Andover Democrat Barbara L'Italien, publicly called on Rosenberg to step aside "for the sake of the institution" until the investigation is completed.

L'Italien told reporters she did not see how alleged victims could come forward during the investigation if Rosenberg was still presiding over the Senate. She also said it would be difficult for the Senate to conduct normal business under the circumstances.

Another Democrat, Sen. Michael Barrett of Concord, said it was unfair to ask Rosenberg to step aside over allegations against his spouse.

Democratic U.S. Sen. Elizabeth Warren also weighed in Monday telling reporters "the charges against the Senate president's husband are disgusting and the people who have levelled these charges have a right to be heard and to be respected and protected."

The scenario unfolding on Monday was without modern precedent in the Senate, leaving many questions as to who would preside over the Senate and how business would operate during Rosenberg's leave from the presidency.

Rosenberg said Friday that Hefner would soon enter treatment for alcohol dependency.

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Associated Press writer Steve LeBlanc contributed to this report.

News from © The Associated Press, 2017