Genson said Monday as he left his downtown Chicago office that Blagojevich had retained him.
Genson has been highly sought after by the rich and famous for his persuasive powers with jurors. His clients have included R&B superstar R. Kelly and Hollinger International media mogul Conrad Black.
Blagojevich is charged with trying to profit from his power to appoint a replacement for President-elect Barack Obama's vacant U.S. Senate seat, among other things.
On Monday, the Illinois House Speaker Michael Madigan announced that he will appoint a special committee to review the case and recommend whether Blagojevich should be impeached. Once the committee makes a recommendation, the full House will decide whether to file impeachment charges against the governor.
"We're going to proceed with all due speed, but we're going to make sure that what we do is done correctly," the Chicago Democrat said.
Republicans and Democrats alike have called for Illinois lawmakers to begin impeachment proceedings against Blagojevich, saying the step is necessary to restore public confidence in state government.
"This isn't about the legal process, this is about the governor being unable to govern right now," Illinois Rep. Jan Schakowsky said on CBS' The Early Show.
"The General Assembly must move to impeach Rod Blagojevich immediately," said DuPage County State's Attorney Joe Birkett, a potential Republican candidate for governor in 2010.
Madigan did not join the chorus of officials calling for Blagojevich's resignation or say whether he thinks the governor should be impeached, saying he should remain neutral because he would preside over any impeachment debate.
But he did not back away from his role as one of the governor's harshest critics, saying he's not surprised by the federal allegations. Madigan, who once co-chaired Blagojevich's re-election campaign, often has refused to meet with Blagojevich or return his phone calls in recent months.
"I've had a chance to get to know Mr. Blagojevich over six years, so I was not surprised," Madigan said. "In light of what we've all seen ... how can anyone be surprised?"
Legislators met Monday afternoon for the first time since Blagojevich was arrested last week on charges he shook down businesses seeking state deals and tried to profit from his power to choose a replacement for President-elect Barack Obama's vacant Senate seat.
The legislative session's focus was supposed to be about considering a special election, but impeachment was the chief topic of conversation.
One survey shows 80 percent of state lawmakers support impeachment, reports CBS News correspondent Dean Reynolds.