RUTHFULLY YOURS

“If you don’t have a thick skin, I’m not sure why you’re in politics,” Mr. Casten says, after we duck into a quiet corner during an office-park meet-and-greet. “What Roskam is offended by is that I’ve had the temerity to speak truth to power. He’s voted 94% of the time with Trump. He has on his website that he is proud to work at Denny Hastert’s desk. I’m opposed to pedophilia. If that bothers him, that’s between him and his God.”

Say what?

To back up a smidge: Mr. Casten is referring to an old press release, from 2011, on Mr. Roskam’s official website. It explained that Dennis Hastert, who served as House speaker from 1999-2007, was passing down a “historic desk” used by Illinois congressmen since the 1940s. Five years after bequeathing the antique, Mr. Hastert admitted he had sexually abused boys as a high-school wrestling coach in the 1960s and ’70s. And this horrifying crime now reflects on Mr. Roskam . . . how, exactly?

Welcome to Illinois’s Sixth Congressional District, where the political debate this year is peppered with casual references to Nazis, morons and, yes, pedophiles. These Chicagoland suburbs, which went for Hillary Clinton by 7 points in 2016, are a prime pickup opportunity for Democrats. The district, shaped like a cocktail shrimp, arcs between O’Hare Airport and the particle accelerator at Fermilab. Half of adult residents went to college, one-fifth have a graduate degree, and the median household earns $99,000.

But a journalist who parachutes into the Sixth District, expecting to write about tax policy or health care, soon ends up pondering stranger questions: Is civility simply outmoded in 2018, the equivalent of bringing a flintlock musket to a gunfight? Even in the Midwest’s tree-lined suburbs, which are full of the educated women who fled the GOP under Donald Trump?

Mr. Roskam, whose harshest censure is occasionally to call his opponent “obtuse,” doesn’t think so. “It’s primarily moms who are the guardians of civil discourse,” he tells me at a tiny Dunkin’ Donuts in Elk Grove Village. “They’re not impressed with the president, who tweets the way he tweets. And they’re not impressed by my opponent, who tweets the way he tweets.” A minute later, he adds: “What I’m communicating to them is, ‘I’m not going to embarrass you like that.’ ”

But in these heady days, who’s embarrassed? On Tuesday the president of the United States, writing on Twitter , insulted a stripper, who claims to have had an affair with him and then unsuccessfully sued him for defamation, by calling her “Horseface.” Democrats, incensed by Mr. Trump, the confirmation of Justice Brett Kavanaugh and much else, have shouted GOP officials out of restaurants and picketed their front lawns. Rep. Maxine Waters, whose Democratic constituency near Los Angeles gave Mrs. Clinton 78% of its vote, made headlines a few months back by expressly endorsing these kinds of tactics.

What makes Mr. Casten’s fiery message notable is that he is trying to win a swing district. Most politicians, as Election Day approaches, water down their rhetoric to attract independent voters. Mr. Casten keeps pouring 100-proof whiskey. When the Trump administration this summer was separating families of illegal aliens, he said in a Chicago Tribune debate that “we are literally kidnapping babies at the border.” At the suburban Daily Herald last month, he said wealth inequality is, historically speaking, “getting dangerously close to the levels that precede revolutions.” The same day he repeated a conspiracy theory that an attorney—reported to be of Mexican and Jewish descent—was “flashing white-power signs behind the Brett Kavanaugh hearings.”

A political newcomer, Mr. Casten pitches himself as a truth-teller in an age of alternative facts. He spent his career fighting climate change while making a profit by capturing wasted energy at factories or converting coal utilities to natural gas. He says he voted for George H.W. Bush and Bob Dole, but he characterizes today’s GOP as complicit in the rise of a demagogue. “This isn’t partisan,” he tells a crowd of about 100 in Elgin, “to call out misogyny, to call out racism, to call out the fact that there was an actual member of the Hungarian Nazi Party in the White House.” (Mr. Casten is referring to Sebastian Gorka, a former Trump adviser, who denies having Nazi connections or anti-Semitic views.)

Even beyond Mr. Trump, the two Sixth District contenders don’t agree on much. Mr. Roskam, a fairly conventional Republican, has voted to repeal and replace ObamaCare. He describes himself as pro-life. He helped write last year’s tax reform and says it’s working, “no question.” He cites a visit to a manufacturer in Downers Grove, during which his hosts pointed out $4 million of new equipment: “They said the only reason they bought it this year was because of the tax reform—full expensing.”