State Sen. Don Harmon, the new Illinois Senate president, expressed bewilderment when asked why documents from his clout-heavy law firm were among the items seized by federal agents from then-state Sen. Martin Sandoval’s office in September.

“I have no idea,” Harmon said recently.

But he offered a theory.

“It’s no secret that former Senator Sandoval and I did not get along, and he had a habit of keeping files on his political opponents,” the Oak Park Democrat said. “For all I know, that’s what it could be.”

Sandoval resigned from office effective Jan. 1 and pleaded guilty Tuesday to taking payoffs to protect the interests of the red-light camera contractor SafeSpeed, LLC.

Sandoval was able to provide cover for the Chicago company because, as chairman of the state Senate Transportation Committee, the Chicago Democrat was the gatekeeper for legislation affecting the industry, court records show.

Harmon declined an interview request but answered questions by email, through a spokesman.

Asked about the Sept. 24 raid on Sandoval’s Springfield office, Vincent Pinelli, one of Harmon’s partners in the Loop law firm Burke Burns & Pinelli, said via email that “we don’t know what, regarding this firm, was taken in the raid or how it got there. Those questions would have to be answered by Sandoval. What I can tell you is that this firm has not been contacted about or had any involvement with Sandoval or the Sandoval investigation.”

The Sandoval search warrant doesn’t name the law firm.

But documents from Burke Burns & Pinelli were among the items federal agents seized from Sandoval’s office, records show.

Other records show the law firm frequently has done business with Illinois state government, which Harmon now helps control. It also has ties to the leader of the other legislative chamber, Illinois House Speaker Michael J. Madigan, D-Chicago.

Madigan has a longstanding relationship, sources say, with one of the firm’s founding partners — Edward J. Burke, brother of the late Mayor Jane Byrne and a campaign contributor to the speaker. Campaign-finance records show Burke and other lawyers at the firm collectively have given Madigan more than $285,000 over the past three decades.

Madigan registered with the city of Chicago in 2001 and 2002 to lobby on behalf of Burke Burns & Pinelli, though City Hall no longer has records to show what Madigan did for the firm.

“Burke Burns & Pinelli was never a client of Mike Madigan or Mike Madigan’s law firm,” according to Steve Brown, the speaker’s spokesman. “The reason he had to register as a lobbyist is because Mike Madigan had recommended the firm to the city for bond counsel work, which the firm never got.”

Before he was first elected to the Senate in 2002, Harmon was deputy legal counsel for Madigan in the House.

Harmon was elected Senate president by the Democratic-controlled chamber on Jan. 19, succeeding John Cullerton, who abruptly resigned after more than four decades in office.

On Jan. 21, Sun-Times reporters tried to contact Harmon about whether his law firm’s business with state government would pose conflicts of interest for him as Senate president.

Though he didn’t respond, he appeared the following day on WTTW-TV’s “Chicago Tonight,” where he said he would be “stepping away” from his law firm.

“We’re working out all those details, but I’ve recognized that I just don’t have the time capacity to be a good Senate president and to practice law the way I practiced it,” Harmon said on the TV news show.

Asked then about federal agents seizing documents related to his law firm, Harmon said Sandoval “had a bad habit of doing opposition research on people he thought were rivals. At the same time, I have no reason to think it was anything but an empty file folder. And, to my knowledge, the firm has no involvement whatsoever.”

In response to subsequent questions about his departure from the firm, Harmon told the Sun-Times by email: “No salary. No deferred compensation. No exit package. We are working out the details, but it will be soon. I was always an employee and never had an ownership stake in the firm.”

If any state government matters related to the law firm come up in the future, Harmon wrote, “I will work to avoid conflicts as I always have.”

In 2017, the Sun-Times reported Harmon’s firm had been paid more than $9 million over the preceding five years for doing legal work for state agencies, government workers’ pension funds and municipal governments whose residents he represents in the Senate.

The legal work involved more than 20 government bodies, including the city of Chicago, Cook County, the Metropolitan Water Reclamation District of Greater Chicago and the agency known as McPier that owns McCormick Place and Navy Pier.

As a state senator, Harmon has voted on the budgets of some of those agencies, including the Illinois Department of Transportation. His firm also has represented government pension funds regulated by Harmon and other legislators as well as the village of Rosemont, one of the suburbs he represents in the Senate.

Harmon said at the time that he got no “financial benefit from state or state-affiliated work done by the firm” and that he didn’t handle government legal work himself; other lawyers at his firm did.

In 2012, Harmon voted on a casino bill that his law firm helped write for the city of Des Plaines, according to a news report.

Harmon’s wife Teresa Wilton Harmon is the managing partner of Sidley Austin LLP’s Chicago law office, which does “a small amount of work” for two state agencies, according to a source who said, “Teresa does not do work for the state and will not be doing work for the state.”

Teresa Harmon said in a written statement: “I am thrilled for my husband and, as an Illinois resident, excited for the work he will do as President of the Illinois Senate. His new role will have absolutely no impact on my legal practice or my firm.”