The federal criminal probe into Commonwealth Edison is one of the most aggressive anti-corruption efforts to permeate Illinois politics in a generation.

Exhibit No. 1 is the middle-of-the-day FBI and IRS raid of Democratic state Sen. Martin Sandoval’s office in the Illinois Capitol in late September. Investigators sought information about four unidentified officials at Exelon, ComEd’s parent company, and documents pertaining to utility rate hikes.

The federal scrutiny even has extended all the way up to the state’s most powerful politician, Democratic House Speaker Michael Madigan, though the veteran lawmaker has not been accused of criminal wrongdoing.

No one has been charged with a crime. But the investigation is broad, complex — and moving fast. Here’s what you need to know to catch up.

The feds are looking into ComEd’s lobbying and hiring practices.

Following a WBEZ/Better Government Association story in July, Exelon went on to disclose that both it and ComEd have received two subpoenas — or legal demands for documents — from the feds. One sought information about the companies’ lobbying practices in Illinois, and another sought communications between the companies and Sandoval.

WBEZ was the first to report that it’s not just ComEd’s lobbying practices that are under the microscope. The feds are investigating whether Commonwealth Edison made politically motivated hires in exchange for favorable government actions — including rate increases that affect how much you pay for electricity.

Authorities believe many of those clout hires got paid but did little or no work, and some of them have ties to Madigan.

Then on Halloween, Exelon disclosed that it’s facing even more federal heat: The U.S. Securities and Exchange Commission, which watchdogs publicly-traded companies, also has launched an investiation into both companies’ lobbying activities.

ComEd is a major player in Illinois politics.

As a utility, ComEd is regulated by state officials and lawmakers. So the power company employs a powerhouse list of influencers at the state Capitol in Springfield.

So who are these lobbyists? It turns out ComEd hired many former aides to Madigan, the powerful House speaker who also heads the state’s Democratic Party.

That roster is rivaled only by a handful of other conglomerates. This year alone, ComEd and Exelon Generation lobbyists have reported spending more than $47,000 wining and dining legislators, state records show.

That total is more than what Springfield heavyweights including the Illinois Chamber of Commerce, AT&T, the Illinois State Medical Society, Comcast, the Illinois Education Association, Caterpillar and State Farm have spent on lobbying expenses this year — combined.

One ComEd lobbyist under federal scrutiny is a Chicago mover and shaker.

One of ComEd’s biggest lobbyists was Jay Doherty. He’s the president of the City Club of Chicago, which is a public affairs nonprofit that hosts regular luncheons where politicians like Mayor Lori Lightfoot, Gov. JB Pritzker and even Donald Trump have been keynote speakers.

Doherty also has lobbied for ComEd for the past eight years — that is, until last week.

He cut ties with ComEd after WBEZ reported that the City Club’s office was raided by the feds back in May (he’s kept his post with the City Club, though). WBEZ also obtained federal paperwork in which ComEd disclosed that it’s paid Doherty $3.1 million between 2011 and 2018 — far more than what Doherty has previously disclosed.

Another lobbyist had been the most influential Illinoisan you’ve never heard of.

Michael McClain isn’t a household name, but he’s been described as an “insider’s insider” because of the sway he once held in Springfield — due in no small part to his close relationship with Madigan.

McClain retired from lobbying for ComEd in 2016 and stopped registering with the state.

Despite his retirement announcement, a WBEZ/Better Government Association investigation showed ComEd still paid McClain $361,000 over 2017 and 2018 for “legal services,” even though he no longer had an active law license.

ComEd has said it “mislabeled” the payments to McClain, and that they were for “political consulting services.” The utility has not specified what that work entailed.

WBEZ has learned that McClain’s home in downstate Quincy was raided by the FBI in May, and the Chicago Tribune reported this week that agents had been wiretapping his phone.

The feds are interested in Madigan himself.

Madigan has not been charged with wrongdoing, and he recently told reporters in Springfield that he’s not the “target of anything.” But it’s now clear the feds have sought information about Madigan on several fronts.

On the same day in mid-May, agents raided the City Club and an ex-Chicago alderman’s home — searching, in part, for records relating to Madigan. They also executed search warrants on two close Madigan allies: McClain and Kevin Quinn, a Southwest Side political operative.

In ComEd’s last major legislative push in 2016, Madigan did not vote on the measure. In 2011, on another big ComEd bill, Madigan was a supporter.

Tony Arnold and Dave McKinney cover state politics for WBEZ. Investigative reporter Dan Mihalopoulos contributed.