By itself, the outcome of the 2024 election in Wisconsin tells us very little about which party has the upper hand in America’s most persistent battleground.
Wisconsin was the closest state in the country this fall.
Republicans won the presidential contest by a hair. Democrats won the U.S. Senate race by a hair.
But under the surface, there’s a political trend line that’s quite troubling for one side (Democrats) and tantalizing for the other (Republicans).
And that involves the changing partisan makeup of this famously purple state, which has shifted steadily in a Republican direction during the Trump era.
As recently as 2016, Democrats enjoyed a 6-point edge in partisan identification in Wisconsin, according to extensive polling by the Marquette University Law School.
During Donald Trump’s first term, however, that morphed into a 2-point Republican advantage.
And during Joe Biden’s presidency, it has grown to a 4-point GOP edge. Over the past two years of Marquette’s polling in Wisconsin (based on almost 8,000 interviews), 46% of registered voters identify with or lean toward the Republican Party, and 42% identify with or lean toward the Democratic Party.
This is a pretty remarkable eight-year shift. But it has been largely obscured by the perpetual closeness of statewide elections here, and the fact that Democrats have been winning them more often than losing them.
We’ve grown very used to thinking of Wisconsin as a “pure” 50/50 battleground, and it certainly keeps voting like it. It has now seen six races for president, governor and U.S. Senate decided by a point or less in the past eight years.
But right now, Wisconsin is not a 50/50 state in its partisan makeup. Over the past decade, it has undergone a net shift of 10 points in party ID from a Democratic-leaning electorate to a Republican-leaning one.
“The confidence of thinking you’re the majority party should not belong to Democrats,” says Marquette pollster Charles Franklin, noting that Democrats haven’t enjoyed an edge in party ID in Wisconsin since 2016.
The GOP’s growing partisan advantage here (which mirrors a nationwide shift toward Republicans) raises all sorts of political questions.
What kinds of voters in Wisconsin have moved away from the Democratic Party?
How have Democrats remained as competitive as ever in statewide races while fewer and fewer voters identify with the party?
How durable is the GOP’s current edge in party ID?
And at what point will it translate into more Democratic losses and more Republican victories at the polls?
Let’s take these one at a time.
First, an explanation of the underlying poling data, which Franklin pulled together for this story. The Marquette Law School Poll has been around since 2012, conducting more than 80 statewide surveys and interviewing more than 70,000 Wisconsin voters. Since there is no registration by party in Wisconsin, polling provides our best measure of the state’s partisan makeup, and the Marquette survey is by far our biggest and oldest polling resource.
Every Marquette survey asks registered voters, “Do you usually think of yourself as a Republican, a Democrat or an independent?” If they answer “independent” or “don’t know,” voters are asked if they think of themselves as closer to the Republican Party, the Democratic Party, or “neither.”
For this analysis, Franklin counted as Republicans people who called themselves Republicans in response to the first question, as well as self-described independents who answered the second question by saying they were closer to the Republican Party. He did the same with Democrats.
Here are the partisan breakdowns of the Wisconsin electorate since the poll began in January 2012, combining all the surveys within each election cycle to get larger and more reliable samples. (Each set of numbers below is based on at least nine polls in that cycle and interviews with at least 7,000 registered voters):
∎ 2012: 43% Republican, 48% Democratic, 8% independent (5-point Democratic edge).∎ 2013-14: 42% Republican, 47% Democratic, 9% independent (5-point Democratic edge).∎ 2015-16: 42% Republican, 48% Democratic, 9% independent (6-point Democratic edge).∎ 2017-18: 45% Republican, 45% Democratic, 9% independent (no edge for either party).∎ 2019-20: 46% Republican, 44% Democratic, 9% independent (2-point Republican edge).∎ 2021-22: 46% Republican, 43% Democratic, 10% independent (3-point Republican edge).∎ 2023-24: 46% Republican, 42% Democratic, 12% independent (4-point Republican edge).
As these numbers show, Democrats had a steady advantage in party ID of 5-6 points from 2012 through 2016, the last five years of the Obama presidency. They lost that advantage during Trump’s presidency and fell further behind during Biden’s presidency. Since 2012, there has been a 6-point drop in self-identified Democrats, a 3-point increase in Republicans and a 4-point increase among “pure” independents.
These are not trivial, snapshot-in-time changes. Party identification “is a pretty stable fact,” says Franklin. “People don’t just wake up every morning and reconsider their party ID as if they never had one. There is a real stickiness to it.”
The polling also shows that these shifts have been unusually big among certain segments of the electorate. In demographic terms, the GOP’s biggest gains by far have been with non-college white men, who have gone from 50% Republican/41% Democratic in 2012 to 57% Republican/32% Democratic in 2024.
Non-white voters without college degrees have also shifted in a GOP direction, especially men. (“Non-white” combines a lot of different groups, but because Wisconsin is overwhelmingly white, we don’t have samples big enough to break out specific data here for Black or Hispanic voters).
In geographic terms, the biggest shifts have happened in the state’s western and northern counties — basically, the parts of Wisconsin that lie outside the state’s three big media markets of Milwaukee, Madison and Green Bay. Collectively, these mostly rural areas have gone from 43% Republican/47% Democratic in 2012 (a 4-point Democratic edge) to 50% Republican/37% Democratic in 2024 (a 13-point GOP edge).
Unsurprisingly, these are the same regions where Republican candidates have made their biggest election gains in the past decade.
More: Donald Trump took Wisconsin in 2024 presidential election by scoring broad gains, and by stemming Republican bleeding in suburbs
Democrats’ victories obscure voter shift in Wisconsin
But on a statewide level, the relationship between Wisconsin’s growing Republican edge in party ID and its actual voting history is a bit of a puzzle.
In fact, since the Democrats lost their edge in party ID during the 2018 election cycle, they have won both races for governor (2018 and 2022); won two out of three U.S. Senate races (winning in 2018 and 2024 and losing in 2022); and split two presidential contests (winning in 2020 and losing in 2024). Republicans have enjoyed a measurable and increasing edge in party ID since the 2020 election cycle but have continued to struggle in big statewide elections to reach or exceed 50% of the vote.
Why haven’t these changes in the state’s partisan makeup translated into more, and bigger, GOP victories (or Democratic defeats) in major statewide contests?
One way to think about this is that when a party’s voters are outnumbered in the electorate, it is essentially swimming upstream. It can only overcome that disadvantage in partisanship in a handful of ways at election time. It can turn out a higher share of its own voters than the other party. It can be more unified than the other party (for example, if the Democratic candidate wins 95% of Democratic voters but the Republican candidate wins only 90% of Republican voters). Or it can win independent voters.
This is actually how Republican Scott Walker won three elections for governor in 2010, 2012 and 2014, back when Democrats enjoyed an edge in party ID in Wisconsin. Walker was very good at mobilizing Republican turnout. He mostly unified Republican voters. And exit polls suggest he won the independent vote. As a result, he not only carried what was a Democratic-leaning state, but he won by bigger margins (5 to 7 points) than any Republican has in the Trump era.
Something similar appears to be going on with Democrats now that they face a deficit in party ID in Wisconsin.In the 2020 presidential race in Wisconsin, won by Biden over Trump, the Democratic vote was more unified than the Republican vote. Fewer Democrats “defected” to vote for Trump than Republicans “defected” to vote for Biden, according to pre-election polls and election-day exit polls. Polling also suggests Biden won the independent vote that year.
In the 2022 race for governor, Democrat Tony Evers won the independent vote over Republican Tim Michels, according to the polling.
And in 2024, Baldwin narrowly survived her race against Republican Eric Hovde by winning independent voters and by keeping her own party base a little more unified than Hovde did, polls suggest.
More: Gilbert: Wisconsin’s Donald Trump-Tammy Baldwin split election explained
Given the Democrats’ growing disadvantage in partisan identification in Wisconsin, you could argue they’ve “over-performed” in statewide races (not down-ballot) in the past three election cycles, either thanks to the strength of their own candidates, the weakness of their opponents, or their ability to organize and turn out their voters.
A growing problem for Democrats means opportunities for Republicans
But the 2024 election also points to why this is a serious ongoing challenge, and why the state’s shifting partisan makeup poses obvious problems for Democrats and opportunities for Republicans.
First, the GOP’s edge in party ID has continued to grow over time, Marquette’s polling suggests. This really sunk in for me when Marquette released its final pre-election poll this year. It showed Vice President Kamala Harris with a tiny 1-point lead in Wisconsin, not far off her tiny losing margin of nine-tenths of a point.
But the eye-opener was the party breakdown in Marquette’s final Wisconsin sample: Republicans had a 4- to 5-point edge in party ID, which is considerably different from the 1- or 2-point GOP edge in party ID we were used to seeing in the 2020 and 2022 cycles.
Could the pre-election polling have overstated the Republican edge in party ID? Maybe. But several things argue against it.
One, Republicans actually did slightly better — not worse — on Election Day than they did in Marquette’s pre-election polls. Two, you also find a 4-point GOP edge in party ID if you combine all the Marquette polling in the 2023-24 cycle. Three, the final Wisconsin exit poll of actual voters (done for the networks) showed a similar 3-point GOP edge in party ID. And finally, numerous other pollsters have found a marked national shift in party ID toward the GOP.
So, the polling evidence is pretty strong that the electorate has become more Republican in Wisconsin and elsewhere.
This means that all things being equal (the two parties are equally unified, equally effective at turning out their voters and equally effective at winning independents), Democrats are now disadvantaged in statewide elections here.
Does that mean the Republican-backed candidate in the huge state Supreme Court election this coming April is destined to win? No. Democrats have had a lot of success mobilizing their vote in recent court elections, and turnout will be a huge factor in that contest.
Does it mean Republicans are likely to win the governor’s race in 2026? Not necessarily. Mid-term elections are often challenging for the party in power in Washington (Republicans). In fact, if Trump’s popularity suffers, that might start to reverse his party’s gains in party ID.
But we don’t know how the Trump presidency will fare.
We do know that over time, Wisconsin’s political make-up has gradually shifted in a Republican direction. And while the state’s partisan makeup doesn’t dictate the outcome of any single election, it determines the playing field on which candidates compete.
And as long as the GOP’s current edge in party ID in Wisconsin endures, it’s hard to imagine that Democrats won’t begin to pay a bigger price for that in big elections.
This article originally appeared on Milwaukee Journal Sentinel: Gilbert: The Wisconsin polling data that should trouble Democrats
