Population changes shape state politics
Wisconsin’s population growth over the past 10 years is overwhelmingly concentrated in three places, according to Census estimates for U.S. counties released this month.
One is very blue (Democratic) in its politics: Dane County.
One is very red (Republican): the “WOW” counties north and west of Milwaukee — Waukesha, Ozaukee and Washington.
And one is pretty purple: the “BOW” counties of the Fox Valley — Brown, Outagamie and Winnebago.
Dane County accounted for 44% of Wisconsin’s total population growth from 2010 to 2020, according to these
latest numbers. The WOW counties accounted for 17%. And the BOW counties accounted for 23%. Together, they generated 84% of the state's growth over the decade.
While these three regions differ in their politics, they did have one thing in common in the 2020 election: all of them shifted away from Republican Donald Trump.
Trump did five points worse in Dane last fall than he did in 2016, losing it by more than 52 points instead of 47.
Trump did five points worse in the WOW counties than he did in 2016, winning them by 23 points instead of 28.
And he did 3 points worse in the BOW counties than he did in 2016, winning them by 7 points instead of 10.
This is one of the sobering facts for Republicans in the new county-bycounty population estimates for Wisconsin: of the 10 counties that added the most people over the past decade, the GOP's performance declined in each one of them between 2016 and 2020.
Meanwhile, of the 38 mostly small Wisconsin counties where Trump gained ground in 2020, 24 of them lost population over the past decade.
In fact, the top 20 Wisconsin counties for Trump saw a net population decline of around 4,000 people in those 10 years.
These trend lines suggest some longterm demographic challenges for Republicans.
Advantage Democrats? Not so fast
But there are sobering facts for Democrats in the same data.
One is that ultra-blue Milwaukee, the state's biggest county, was a population loser for the decade.
Another is that while Dane is the highest-growth county in the state, most of the other top-growing counties in Wisconsin lean Republican, which is offsetting some of Dane's political impact. Because of their growth, some of these red counties are delivering bigger raw vote margins for Republicans even as Republicans are getting a smaller share of their vote.
For example, Trump's point margin in Washington County dropped from 40 to 38 points between 2016 and 2020. But because the county's total vote grew, Trump's raw vote margin was almost 3,000 votes bigger in 2020. Something similar happened in St. Croix County in western Wisconsin.
Politically speaking, these population trends are a mixed bag. They aren't uniformly helpful to one party or the other.
If you “replayed” the 2020 election with the same vote margins in each county but applied another four years of the current growth trends, the vote in 2024 wouldn't look much different. The Democratic winning margin in Wisconsin (which was 20,608 votes last year) would grow only slightly, by about 1,500 votes.
In other words, the current growth trends may be marginally helpful to Democrats in the short run.
But the bigger reality is that from one election to another, population shifts by themselves don't have a major impact on the vote, especially in a state like Wisconsin, which isn't growing very fast.
In fact, they have far less impact than changes in turnout or swings in voter sentiment. How much a region is growing or shrinking matters a lot less in a given election than whether that region is shifting politically, or turning out at lower or higher levels.
The 2016 election is a great illustration of this.
According to census estimates, 39 Wisconsin counties lost population between 2012 and 2016.
Republican Mitt Romney won these mostly small counties by a combined 10,000 votes in 2012. Then these GOPleaning counties lost about 13,000 people over the next four years.
Not a healthy development for the GOP, right?
Except that Trump went on to carry these same counties by almost 124,000 votes in 2016 — 12 times Romney's margin. In other words, a massive rural political shift toward the GOP had far more impact on the election than the fact that these rural areas were losing population.
Four years later, many of these small no-growth counties generated even bigger vote margins for Trump, because they experienced a disproportionate increase in turnout. Voters who stayed home in 2016 came out for Trump in 2020.
There's a telling example on the Democratic side as well. Milwaukee County lost about 10,000 people between 2016 and 2020, according to the latest census estimates. Pretty bad news for Democrats, right?
Except that the Democrats' winning presidential margin in the county grew by about 20,000 votes — from roughly 163,000 in 2016 to around 183,000 in 2020. In this case, a sizable political shift in Milwaukee's inner suburbs toward Democrats had a much greater impact on the county's vote than its population decline.
In the first case, a bunch of small red counties got smaller but packed a far bigger electoral punch for Republicans than they ever had in the past. In the second, a big blue county got smaller but delivered a bigger vote margin for Joe Biden than it ever did for Hillary Clinton or Barack Obama.
Political shifts trumped population change.
Ideally, of course, both parties would like their base counties to be simultaneously adding lots of people AND growing more lopsided in their support.
The Dane County effect
But Dane County is the only county in Wisconsin where that is happening. That's why Dane is having more impact on the state's electoral math than any other county. Its political shifts and its population shifts are not only dramatic, but they're working in the same direction politically.
That's quite different from what's occurring elsewhere.
The Republican WOW counties are growing modestly (by a combined 4% over the decade) but getting less Republican. Republican St. Croix County, on the periphery of Minnesota's Twin Cities, is growing faster (9% over the decade) but has also become less Republican. The Fox Valley is growing (6% over the decade) but is fairly purple and not trending sharply in either direction. Milwaukee County has gotten bluer but a little smaller. Much of central, northern and western Wisconsin has gotten very Republican (and may get a little more so) but is flat or declining in population.
None of this seems very predictive of where the perennially competitive battleground of Wisconsin is headed politically, either in 2022 or 2032.
This isn't a picture of a state getting unmistakably bluer or redder.
It seems instead like a recipe for more of the same.