DETROIT, MI — An average time-on-page of nearly 17 minutes. Nearly 50,000 users and 100,000 pageviews, with more than 50 percent of those pageviews from the mobile site or mobile appsfor long stories studded with graphics and interactives. Fifty-two percent of the audience between ages 25 to 34. And an almost incredible bounce rate of .08 percent.

Even as the debate over Web analytics and how best to measure “engagement” continues, that’s a set of numbers that will make any news editor sit up and take notice. The journalism that produced it? “Dividing Lines,” an exhaustive, densely analytical, data-rich four-part series (one, two, three, four) on partisan polarization in metropolitan Milwaukee, produced this month by the Milwaukee Journal Sentinel. Don’t let anyone tell you that wonky political reporting won’t play on the Web—or that it only works in Washington.

The response to the series was “extraordinarily gratifying,” said Thomas Koetting, the paper’s deputy managing editor, who provided metrics to CJR. “People feel like they need this kind of deep information to have intelligent conversations and move the region forward.”

It no doubt helped that, while there are always nits to pick with an effort this ambitious, the series was extraordinarily good—as political journalists around the country were quick to acknowledge. It painted a compelling, and in many ways worrying, picture of a region that is a microcosm of American politics, only distilled and amplified. Partisan polarization, political segregation, and relentless, seemingly intractable conflict have grown across the country over the past generation. Nowhere is that more true than in bright-blue Milwaukee and its deep-red suburbs, which are like rival base camps for the many high-stakes campaigns that roiled Wisconsin over the past few years—including the election, recall, and re-election of Gov. Scott Walker, who understands the dynamic as well as anyone. As reporter Craig Gilbert wrote in the opening of the series: “In its ultrapartisan geography, this is arguably the most polarized place in swing-state America.”

And as Part 3 of “Dividing Lines” makes clear, while that dynamic has real downsides, it paradoxically spurs political engagement—which would have helped whet reader appetites for this sort of granular coverage. A few other unique ingredients were in place as well. In Gilbert, whom CJR dubbed “the most political science-friendly reporter in America,” the Journal Sentinel had a veteran journalist who had witnessed the striking rise in polarization since the 1980s firsthand and documented much of it on his Wisconsin Voter blog. The series was published on a new responsive project template that allowed the paper’s online producers to incorporate interactives and other media inline, unpacking the data where it made the most sense, while also featuring related content. And it was supported by the Marquette University Law School, which is cultivating a role as a leader of civic conversations.

In short: The series represented a major investment, it was the right story for the right time and place, and it was a success.

Which is not to say it was easy. While the series tracks a changing political culture, there are no central characters whose personal narratives pull the reader through. For this sort of work, “the writing is harder than just telling a story,” Gilbert said. Gilbert and Koetting mulled over just about “every word in every phrase,” the editor said, in order to make the writing as clear as possible. The result is clean but dense, sometimes demanding but often rewarding. Even in Milwaukee, the result may not be for everyone (I would have liked a little more narrative myself, and the bland video interviews with voters were one of the few disappointments). It certainly wasn’t optimized for Facebook. But there’s a substantial audience that read every word.

“What we discovered is we need to give readers some credit,” Gilbert said. This is political journalism, he said, that is “not about what both sides say about one another, but is driven by authority because it is fact-based.”

Reader engagement and understanding was supported by some outstanding graphics and interactive maps, created by Allan Vestal, that made the seemingly bottomless data digestible and relieved Gilbert of some of the heavy lifting. And a new project template allowed the paper, for the first time, to incorporate interactive features “within a story as storytelling tools, instead of just as exploratory elements,” said Jennifer Amur, who oversaw the digital design. (In an earlier major series supported by Marquette, interactives and other multimedia open in separate windows. It’s also worth noting here that of course the series ran in print as well, where it would have reached many more readers, even if we don’t have metrics on notes taken in ballpoint pen. Here’s what the first installment looked like on A1.) 

Anna Clark is CJR's correspondent for Michigan, Wisconsin, Ohio, and Pennsylvania. A 2011 Fulbright fellow, Clark has written for The Guardian, Grantland, and Salon; blogs at Isak; and can be found on Twitter @annaleighclark. She lives in Detroit.