Illinois' jailbird governors: Otto Kerner, George Ryan, Dan Walker, and, probably, Rod Blagojevich. (Associated Press/File)

Here’s a good bar bet: Which state has sent the most governors to prison?

If you said Illinois, you win. Rod Blagojevich’s conviction on 17 corruption charges Monday makes him the fourth governor headed to the big house: Otto Kerner got three years for bribery, Dan Walker served seven years for bank fraud and Blago’s predecessor, George Ryan, is serving a 6-and-1/2-year sentence for racketeering. (Ryan was recently released temporarily to be with his terminally ill wife, who died of lung cancer Monday.)

Why Illinois? “It’s a really good question,” said Sol Ross, head of the Illinois State Society in the District. The same place that gave us Abe Lincoln, Adlai Stevenson and President Obama has a century-old history of pay-for-play machine politics.

“We are the capital of corruption in the United States,” said Dick Simpson, head of the University of Illinois political science department. “Businessmen expect to give bribes, and politicians expect to get them.” Governors, he said, are best able to take advantage of the system and therefore more likely to be caught, unlike Chicago mayors, who have more buffers and are smarter about how they do business.

“I often say I worked for three unindicted Illinois governors,” said Jim Nowlan, a former state legislator and expert on state politics. Illinois voters, he told us, view government as something to work around, and they tolerate a certain degree of illegal activity as necessary to get things done. More than 1,500 public officials have been convicted on corruption charges since 1970.

“I have three college roommates all measured for striped suits,” Nowlan said.

Another factor: Chicago dominates the media and political spotlight (Rahm Emanuel dreamed of being mayor, not governor), and what happens in Springfield is almost an afterthought.

Former Maryland Gov. Marvin Mandel hugs his wife Jeanne after his release from prison. (Joe Giza/ Associated Press)

“It may have to do with the internal politics of the state and the people who win nominations for governor,” said AEI political scholar Norm Ornstein. Blago, for example, didn’t impress many when he served in Washington as a congressman. “No one said, ‘He’s a real comer.’ ”

Lastly, Blago was prosecuted by Patrick Fitzgerald, the longest-serving U.S. attorney in Chicago history who also took down Ryan for corruption.

While Illinois tops the conviction list, plenty of states have governors who’ve done time. The exact number isn’t clear: The National Governors Association informed us that they do not keep track of such things. (It does, however, have a Web database that allows you to search bios on all U.S. governors through history. Keyword = “prison”?: 162 results! Alas, most were triggered by phrases like “prison reform.”) Cross-referencing various sources, we counted about 17 governors who’ve gone to prison.

Former Louisiana Gov. Edwin Edwards at a halfway house in January. (Gerald Herbert/ Associated Press)

Alabama, whose former governor Don Siegelman was sent up the river in 2006, seemed like a worthy rival until we eliminated the governors imprisoned by the Union army during the Civil War. Arizona carries a whiff of scandal, yet its troubled guvs didn’t do hard time: Evan Mecham was impeached but acquitted on campaign-finance charges; Fife Symington’s conviction on bank fraud was overturned. Maryland’s got itself quite a reputation but mostly for its local officials: Marvin Mandel is the only governor who got put away — Spiro Agnew never was.

Illinois’s closest corruption rivals appear to be West Virginia and Louisiana, each with two incarcerated guvs — most famously Edwin Edwards, who got out of the pen in January after serving eight years. Due to finish house arrest next week, the 83-year-old has a 30-something fiancee and is exploring a career in reality TV.