Gov. Bruce Rauner read a good book recently, “The Big Sort,” by journalist Bill Bishop.

It’s about how Americans more than ever are choosing to live only with like-minded people. Liberals are flocking to liberal bubbles, conservatives to conservative bubbles, religious folks to religious bubbles and so forth.

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This is bad because, as Bishop writes, when Americans who hold different values and political views don’t live, work and play in the same shared places, they no longer talk and listen to each other. They become strangers to each other and fall into thinking the worst of each other. They lose sight of all they have in common.

Rauner told us “The Big Sort” was a favorite book of his on Tuesday, when he visited the Sun-Times for a debate with his Democratic opponent in November, J.B. Pritzker. There was irony in that because the debate, as it unfolded, became a pretty good example of how modern political campaigns also are tearing us apart. Today’s politics, feeding off our polarization, are both a product and a cause of the “big sort.”

The race for governor is of huge importance to the future of Illinois, which is burdened by billions of dollars of debt and unfunded pension obligations. Rauner and Pritzker have very different ideas about how to solve those problems and others. But too often during the Sun-Times debate, you really had to listen closely to hear those ideas above the din of the personal attacks. On six separate occasions, the candidates talked over each other so much that we couldn’t clearly make out what they were saying.

Rauner, who is behind in the polls, unfortunately played to his base in a way that verged on Donald Trump at a MAGA rally. It wasn’t enough for him to find fault with Pritzker’s positions; he took repeated shots at his opponent’s honesty and integrity.

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A particular low point came when Sun-Times columnist Mary Mitchell, while asking Pritzker a question about personal character, noted that “four of the last nine governors have gone to prison.” Rauner interjected, pointing to Pritzker: “You have number five right here.”

Rauner was referring to the fact that Pritzker once had the toilets removed from a building he owned to gain a property tax break of more than $300,000. That’s a legitimate point of attack against Pritzker. Whether Pritzker broke a law, you would hope that a possible future governor adheres to higher ethical standard.

But for Rauner to paint Pritzker in prison stripes? That was beneath Rauner, just as it was cheap for Rauner to address Pritzker as “Mr. Tax Cheat.”

We urge you to watch the debate for yourself, if you have not already, on our website or Facebook page, and tell us what you make of it. We invited only Rauner and Pritzker to the debate, excluding the other two candidates, believing that a one-on-one discussion between the two major candidates could be of real value to the voters.

On a number of issues that will still matter to Illinois a year from now, such as a graduated income tax, gun laws and the plight of undocumented immigrants, Rauner and Pritzker made their legitimate differences crystal clear. We urge you to ignore the character assassination and hear them out.

We live in culturally and politically polarized times, for sure. But we remain convinced that Americans are not, as a people, nearly as far apart in their hearts and minds as it appears. If only we could share a burger (vegan for you animal rights folks) in the backyard.

But, as Bishop wrote in “The Big Sort,” we increasingly live in bubbles, comforting worlds of like-minded people watching like-minded cable news shows.

Modern political campaigns exploit those divisions, much to the harm of our state and nation, and we think we saw some that in Tuesday’s gubernatorial debate.

What’s the last notable book Pritzker has read, by the way?

He told us it was “Industries of the Future,” by Alec Ross.

Send letters to: letters@suntimes.com.