State Sen. Harriette Chandler, the Senate's majority leader and top deputy, is poised to become the chamber's acting Senate President and replace Stanley Rosenberg amid the whirlwind of turmoil that's enveloped the chamber.Senators will officially vote tonight to name Chandler as its acting leader after Rosenberg announced he is taking a leave of absence from his post in the midst of an internal investigation into allegations of sexual misconduct against his husband.Chandler said she is "resolved" to give up her post if Rosenberg returns. It was also announced that the state Ethics Commission will be instructed to hire an outside investigator -- following a vote to do so at tonight's session of the state Senate -- as Beacon Hill legislators scramble to respond to allegations leveled against Bryon Hefner, Rosenberg's husband. Massachusetts Attorney General Maura Healey and Suffolk County District Attorney Daniel F. Conley also said today they are prepared to open a criminal investigation into the allegations leveled against Hefner. The development adds a new dimension to the firestorm that's engulfed the State House and Rosenberg, who just hours earlier said he was taking a leave of absence from his powerful post amid an internal Senate investigation. In a joint statement, Healey and Conley said the first step is speaking with alleged victims and witnesses. "We ask anyone with this information to contact either office, and we remind every survivor of sexual assault that they can count on us to provide a safe, respectful, victim-centered environment, no matter what the circumstances might be," the statement said. "Sexual assault is a crime and we want to send a clear message that harassment and assault of any kind will not be tolerated." Senators, meanwhile, were huddled in a closed-door caucus in the State House all day before breaking tonight to vote. Rosenberg this morning told senior senators he is taking a leave of absence from his powerful post amid an investigation into allegations his husband sexually assaulted or harassed multiple men."I believe taking a leave of absence from the Senate Presidency during the investigation is in the best interest of the