[9][10] As a federal prosecutor in the early 1970s, he obtained a conviction against former governor Otto Kerner Jr. for his use of improper influence on behalf of the racetrack industry.

[11] He also tried and convicted many of Chicago mayor Richard J. Daley's top aides, most notably Alderman Thomas E. Keane and County Clerk Matt Danaher, on various corruption charges.

People like Keane and Danaher, the mayor's point man on patronage were also major figures in the Cook County Democratic Party's political machine.

He not only prosecuted high-profile Democrats, but also prominent Republicans such as County Commissioner Floyd Fulle and former U.S. Senate candidate, William Rentschler.

[citation needed] In November 1980, Thompson, by his executive order, instituted a hiring freeze for all state agencies, boards, bureaus, and commissions under his control as governor.

Suit was brought and the Supreme Court held this political patronage practice unconstitutional as a violation of the First Amendment rights of low-level public employees in Rutan v. Republican Party of Illinois, 497 U.S. 62 (1990).

In 1989, Governor Thompson agreed to establish a compounding, 3 percent cost-of-living increase for retirees from Illinois government jobs, including public school teachers.

[15] In recent years, the cumulative effect of the 3 percent annual increases has been recognized as one of the major causes of Illinois' public employee pension crisis.

[24] Thompson was also a director and head of the Audit Committee for Hollinger International, the media company founded by Conrad Black, which was the subject of a U.S. Securities and Exchange Commission investigation.

[25] In 2002, he was appointed to serve on the 9/11 Commission, where he aggressively questioned Richard Clarke, the former chief counter-terrorism adviser on the United States National Security Council.

During the 2008 presidential primary campaign, Thompson announced his support for former New York City Mayor Rudy Giuliani for the 2008 Republican nomination.

[26][27][28][29] In a tribute on Twitter, political consultant David Axelrod, who covered Thompson as a young journalist, described him as "one of the smartest and most formidable politicians I’ve ever known.

"[32] It is a reference to Thompson's efforts in 1988 to convince Illinois lawmakers to approve funding of a new stadium for the White Sox, who were threatening to move the club to St. Petersburg, Florida's newly built Suncoast Dome.