In his head, Paul Green curated unrivaled stacks of knowledge about Chicago politics dating back to the 1800s.

As a political analyst, he regularly shared his thoughts on radio, television and in newspapers.

As a professor, first at Governors State University before heading the Institute for Politics at Roosevelt University, he taught generations of students about the “Chicago machine.”

As an author, he delved into City Hall’s fifth floor occupants in a series of books, including one entitled “The Mayors: The Chicago Political Tradition.”

And as chairman of of the City Club of Chicago — a nonpartisan civic group that hosts forums and debates — Mr. Green served dually as a self-deprecating moderator and tough questioner of top local and national political figures.

Mr. Green died Saturday night from an aortic aneurysm, according to his wife, Sharon. He was 73.

Mr. Green experienced pain in his back around dinner time and became flush and dizzy, she said. An ambulance took him to Northwestern Memorial Hospital, where he died a short time later, she said.

In his bio on Roosevelt’s website, Mr. Green called Chicago a “giant political/governmental laboratory.” He urged his students to go into Chicago’s diverse neighborhoods and do political research.

“Paul was a great guy,” said Bonnie Gunzenhauser, the university’s dean of arts and sciences. “He was incredibly well connected and at Roosevelt he was very generous with those connections with students, faculty and alumni. He was happy to share his success and bring other people along whenever he could.”

“He had a great sense of humor,” she added. “He offered incisive analysis with a light touch and never failed to see the entertaining side of politics.”

In 2002, then-state Sen. Barack Obama visited his class to chat with his students.

“He’s been a fixture in the Chicago political scene and the Chicago academic scene for three or four decades now. Most academics don’t really know the details of Chicago politics. He knew it inside out,” said Dick Simpson, a political analyst and University of Illinois at Chicago professor.

“He made an excellent person to debate with,” Simpson said. “Often he would support the machine and I would oppose the machine in its various forms under different mayors.”

“He believed the Democratic Party was uplifting for immigrant groups particularly, and thought it better represented the working and middle class,” Simpson said.

Though he leaned Democratic — even getting his start in politics by volunteering for Robert F. Kennedy’s presidential campaign — his political analysis in the media was unbiased and numbers driven.

“Most of the time he maintained a neutral professional position,” Simpson said.

Chicago heavyweights such as the mayor or police superintendent appeared beside him at City Club events. He never used kid gloves when moderating public forums, especially during question-and-answer sessions.

“He let it rip. A ball was a ball, and a strike was a strike,” City Club President Jay Doherty said.

“He sent me an email yesterday with a list of names for a panel we plan to host on the presidential election in November,” he said.

“The City Club would not be the premier public affairs forum that it is without Paul Green and his intellectual gravitas,” Doherty said.

Mr. Green grew up in neighborhoods on the city’s West and North sides and attended the University of Illinois as an undergraduate before earning master’s and doctoral degrees at the University of Chicago.

“He’s been to 14 conventions,” said his wife. “He lived and breathed that stuff.”

She said her husband planned to write a fourth book in his series on the city’s mayors. It would have focused on Mayor Richard J. Daley.

“Paul said the first Mayor Daley was painted with broad strokes after the riots at the Democratic Convention in 1968,” Sharon Green said. “But he wanted to write about his roots growing up in Bridgeport. His alliance building. Paul liked him a lot.”

Mr. Green worked out at the East Bank Club most mornings, where he would often bump into Mayor Rahm Emanuel, who’s known for his sunrise swims at the River North club.

In a phone call offering condolences Sunday afternoon, Emanuel explained a ritual he shared with Mr. Green.

Emanuel would poke Mr. Green’s newspaper off its ledge while he rode a stationary bike. And, in turn, Mr. Green regularly purloined Emanuel’s newspaper when he’d set it down.

“They’d josh around,” Mr. Green’s wife said.

In a statement Sunday, Emanuel said, “Paul Green was a Chicago political legend and countless people across the city know ‎him as a gifted writer, teacher, historian and analyst. I have known Paul personally for many years, and was always impressed by his capacious intellect, his boundless curiosity, and his quick wit.”

Gov. Bruce Rauner said, “Paul’s unique and humorous style to dissecting the Chicago and Illinois political process will be missed. His reputation as a fair and knowledgable voice will leave a void in Illinois politics.”

In addition to his wife, Mr. Green is survived by his daughter Sarah Green. His son, Robert, died six years ago from a brain tumor.

A public memorial will be scheduled.