Updated: 7:18 p.m.

The top Democrat in the Illinois Senate made the surprise announcement late Thursday afternoon that he plans to retire.

Senate President John Cullerton, D-Chicago, revealed his plans as the General Assembly prepared to adjourn for the year with the conclusion of its fall veto session.

“I’m ready to embark on a new course,” Cullerton was quoted as saying in an emailed statement Thursday night.

“I’ve been promising my wife, Pam that I would retire:

•  after 39 years of duty …
•  when I turn 70 …
•  when we had a Democratic governor …

“So now, after 41 years in the legislature and 40 years of marriage, I’m finally going to live up to my promise to retire,” Cullerton said.

Cullerton’s retirement will take effect in January.

As the cloud of federal corruption probes has loomed over Springfield, Cullerton spokesman John Patterson told WBEZ the Senate president said he is not under investigation. Three members of his caucus have recently been the subjects of federal scrutiny.

Cullerton’s distant cousin, Tom Cullerton, D-Villa Park, was indicted earlier this year for being on the payroll of the Teamsters union despite allegedly not doing any work.

Democratic State Sen. Martin Sandoval, D-Chicago, had his home and office raided by federal agents. A search warrant shows a widespread probe into Sandoval. Sandoval has not been charged with wrongdoing.

And an unnamed state senator wore a wire against former Democratic State Rep. Luis Arroyo, who allegedly offered the senator a bribe in exchange for supporting legislation that would benefit a client of Arroyo’s lobbying business.

Federal agents have not named the senator who wore the wire, though the Chicago Sun-Times and Chicago Tribune have identified him as State Sen. Terry Link, D-Vernon Hills. Link has denied being a mole.

Cullerton’s legislative career began when in 1978, when he was elected to the Illinois House. He moved to the Senate in 1991, when he was appointed to fill the seat vacated by Dawn Clark Netsch.

One of his first acts as Senate president came in early 2009, when he oversaw the impeachment trial of ex-Gov. Rod Blagojevich, which ultimately resulted in the governor’s removal from office.

Cullerton also is a registered lobbyist with the City of Chicago, according to Board of Ethics filings.