CHICAGO (CBS) — Former Illinois House Speaker Mike Madigan is the longest-serving lawmaker in Illinois history, but now, his time in Springfield is coming to an end.

He announced his resignation on Thursday – first to be effective at the end of the month. But he later issued a letter saying his resignation was effective immediately.

READ MORE: Rev. Jesse Jackson Released From Rehab, Family Says He And Wife Are Now COVID-Free

And as CBS 2 Political Investigator Dana Kozlov reported, many saw this outcome as inevitable – and had expected Madigan’s resignation for the past month since he ended his campaign to continue as House Speaker.

Madigan has also had the dark cloud of a federal investigation hanging over his head for almost a year.

In a statement, Madigan simply said he is leaving office at peace with his decision:

“It has been my great honor to serve the people of Illinois as speaker of the House and state representative of the 22nd District. This journey would not have been possible without my wonderful wife, Shirley, and children, Lisa, Tiffany, Nicole and Andrew, who have stood by my side year after year, providing their love and support despite the pressure of growing up in the public spotlight. I am fortunate to have them in my life.”

For half a century, Springfield was Madigan’s kingdom. As the powerful and longest-serving House Speaker in not just the state’s history, but the country’s, Madigan had tremendous influence over what laws passed, who got elected – and, as the head of the state’s Democratic Party, who got campaign money.

But Madigan’s fiefdom began to crumble last summer when he was implicated as “Public Official A” in a scandal in which ComEd officials admitted to paying out bribes and doling out jobs to those who supported him.

In January, Madigan decided not to run for the speakership again, paying the way for Rep. Emanuel “Chris” Welch’s election to the role.

That chain of events fueled speculation that Madigan would soon resign from the Illinois General Assembly altogether.

“It’s impossible to know how much this is related to some of the trouble that’s swirling, and how much of it’s related to, it’s simply time,” said North Central College Professor Stephen Caliendo. “You know, older white guys are probably not the future of Democratic politics.”

READ MORE: Simeon High School Student Jamari Williams Shot And Killed Blocks From School; Classmate Wounded In Separate Shooting In Hyde Park

House Speaker Welch was also not surprised.

“He called me late last night to give me a courtesy heads-up,” Welch said.

But Welch said their conversation was reflective and nostalgic – and nothing more. He said Madigan did not give him any insight as to whether the resignation was connected to the ComEd schedule or why it came now.

Welch called Madigan’s resignation the end of an era.

“I think his legacy is going to be pretty clear, that it’s because of Mike Madigan that we had strong, sustained Democratic leadership here in Illinois,” Welch said.

Welch touts Democratic-led victories under Madigan, such as marriage equality. But critics, including former Gov. Bruce Rauner, have long blamed Madigan for the state’s fiscal woes.

“He has to take responsibility for the difficult financial situation Illinois is in, and he probably gets to take some credit for some of the good things that have happened in this state in the last 30 years as well,” Caliendo said.

While Madigan is leaving the state House, he is still the chairman of the Illinois Democratic Party. Speaker Welch would not say if he thought Madigan should resign from that position as well.

But Caliendo, and others, believe that is just a matter of time too.

MORE NEWS: City To Install Or Upgrade 100 Miles Of Bike Lanes Over Next Two Years

Madigan did not address the future of his chairmanship in his statement, and he declined Kozlov’s request for an interview.