When Trisha and Andy Allcock decided to leave their native Ohio, they set their sights on Wisconsin.
Madison, the second-largest city in the state, and its suburbs in Dane County checked all of the boxes: job opportunities, excellent public schools for the couple’s two children, and hiking and camping within easy reach.
Another irresistible selling point? The dark-blue liberal politics of Dane County.
“We’re very extreme Democrats,” said Ms. Allcock, 43, a marketing executive who said she “absolutely” planned to cast a ballot for Vice President Kamala Harris.
Voters like Ms. Allcock could decide the presidential election in Wisconsin, which flips back and forth between Republicans and Democrats in statewide contests by the slimmest of margins.
Dane County, where Ms. Harris is holding a rally on Friday night, is home to the state government, the sprawling flagship University of Wisconsin campus and, particularly in the last decade, a flourishing health care and technology industry.
It is also the fastest-growing county in the state, changing what it takes for presidential candidates to win a statewide race in Wisconsin. In recent years, Dane County has seen a rapid population rise in both the city of Madison and the suburbs that are suddenly blossoming around it, fueled by growth at the university and the local economy.
The people who are moving to Dane County tend to vote for Democrats, opening an opportunity for a party desperate to win a state that narrowly picked President Biden in 2020 and narrowly picked Donald J. Trump in 2016. Turnout in this region has been sky-high in recent presidential elections, a reflection of the Democratic Party’s ground game in Dane County. In 2020, 89 percent of registered voters in the county cast ballots.
The shifts have not gone unnoticed, and with just over six weeks until the election, Democrats plan to open a 15th campaign office in Dane County on Friday, more than in any other county in the state.
Last week, residents of Middleton, a suburb of Madison, gathered with popcorn in a campaign office to watch Ms. Harris debate Mr. Trump.
Among them was Emily Kuhn, Middleton’s mayor. She noted the signs of the population boom all around: new schools, shopping centers, luxury apartments and subdivisions, built to accommodate thousands of newcomers, both young professionals and baby boomers.
“Dane County is critical,” she said. “It could change the outcome of the election.”
The next day, several miles southwest of the University of Wisconsin campus, volunteers were preparing to fan out to knock on doors and to distribute literature to Democratic voters. Passers-by streamed into a storefront office asking for Harris-Walz yard signs, only to learn that they had all been snapped up.
Jane Bernstein, a volunteer leader who wore a turquoise T-shirt that read “Democracy is a verb,” darted around the room, training canvassers and handing out neighborhood maps.
Ms. Bernstein, a retired high school teacher, helps run one of 23 neighborhood “action teams” in Dane County, groups that for months have been organizing, knocking on doors and trying to find — and lock down — every Democratic voter in the county.
“If we can get Dane County out in very high numbers,” Ms. Bernstein said, “we can essentially outvote the red parts of the state.”
Republicans, recognizing the growing challenge that Dane County poses, say they intend to find every conceivable vote for Mr. Trump, even if they are outnumbered in the area.
Andrew Iverson, executive director of the state Republican Party, said that volunteers are knocking on thousands of doors, making phone calls and sending postcards to targeted voters.
“We just need to improve in Dane County by a few percentage points — that can mean the difference between winning and losing,” he said. “This is the best effort I’ve seen from Republicans in Dane County.”
Demographic changes have scrambled the political calculation for winning Wisconsin.
The population is shrinking in the Democrats’ traditional stronghold of Milwaukee, which remains the largest city in the state with just over 550,000 people but has reached its lowest population since 1920, according to the Census Bureau.
Outside the Milwaukee and Madison areas, in the more sparsely populated regions of the state — dotted with dairy farms, warehouses and small manufacturers — Mr. Trump has proven extremely popular, helping Republicans run up vote margins far higher than in previous elections.
All of it has brought added importance to voters in Madison and its suburbs.
Population growth remains slow through much of Wisconsin, but Dane County, home to 575,000 residents, has seen an increase by 18 percent since 2010, and the pace of growth shows no signs of ebbing.
Thousands of young, college-educated professionals who a decade ago might have flocked to New York City or San Francisco are finding work in a flourishing science and technology sector around Madison.
The changes help explain recent elections.
In 2016, Hillary Clinton won about 148,000 more votes in Madison and its surrounding communities than Mr. Trump did, but not enough to overcome his 171,000-vote advantage in the rest of the state.
In 2020, the fortunes reversed: Mr. Trump ran up a 163,000-vote margin around the rest of Wisconsin, while President Biden won Madison and its suburbs by more than 183,000 votes, winning the state.
In this year’s race, at least one prominent Wisconsin Republican, former Gov. Tommy Thompson, has urged the Trump campaign to search for inroads in the region, despite the numbers.
Mr. Thompson, who held office from 1987 to 2001 and enjoyed broad bipartisan support, said he had appealed to Mr. Trump directly, urging him to work to cut into Democratic margins.
“You cannot just leave Dane County and Madison alone and expect to win an election in Wisconsin anymore,” Mr. Thompson said in an interview from his home in Madison. “You’ve got to come in and compete. I don’t know why Republicans can’t see that.”
But Alex Conant, a Republican strategist, dismissed suggestions that his party’s candidate had anything to gain by campaigning in Madison.
“Trump definitely shouldn’t go anywhere near Dane County — that’s just going to drive Democratic turnout,” Mr. Conant said. “The strategy for the state is, you have to drive up the numbers in the suburbs and rural areas elsewhere because you’re going to get crushed in Dane.”
The growth in Dane County is impossible to miss. Cranes are busy amid the bustle of downtown Madison, constructing high-rise apartment buildings and new campus buildings. In 2022, the Beltline highway, which stretches along some of the fastest-growing suburbs in the area, added a flex lane to ease traffic congestion during peak hours.
The Allcock family, since moving to Middleton in 2017, has seen a new elementary school built nearby to accommodate more students, plus a membership-only swimming pool and a golf course in their neighborhood.
Their house was built in 1977, in an area that is now considered older and well-established. But not far away, new developments are everywhere, with houses quickly pounced upon by buyers.
“It’s like you go through this portal — from old homes to new homes,” Ms. Allcock said.
Companies like Epic, the medical software giant, are headquartered in the Madison area and have been steadily hiring in recent years, bringing in hundreds of engineers and software developers from out of state.
Epic has drawn employees away from the coasts with a no-cubicle policy, a casual dress code and the promise that after five years employees can earn a four-week sabbatical anywhere in the world.
“The majority of roles that we’re hiring, we’re hiring recent grads,” Katie Lee, a lead recruiter for the company, said.
The population boom has not come without growing pains.
Mayor Satya Rhodes-Conway of Madison said that the rising cost of housing in Madison in recent years had sent people who would like to live there — but had been priced out — into Middleton, Fitchburg, Verona, DeForest and other nearby towns.
As more people have migrated to suburban Dane County, they have brought their liberal politics with them.
Charles Franklin, a pollster at Marquette Law School in Milwaukee, said that there was very little drop-off in the Democratic vote in Madison’s suburbs, unlike in the Milwaukee area, which is surrounded by conservative-leaning communities.
“It’s Democratic through and through, and the suburbs are some of the bluest suburbs in the nation,” he said.
In Verona, a community of 15,000 that is home to Epic’s headquarters, an influx of Democratic-leaning residents have brought changes that might feel more familiar in Madison, a short drive to the northeast.
In 2023, a Pride flag was flown outside City Hall in Verona for the first time. In 2020, Kismet Books opened in the heart of town, a shop that a manager, Hailey Morschauser, described as a “queer independent bookstore with a lot of focus on marginalized communities.”
The store receives the occasional piece of hate mail, she said, and an angry woman once stormed into the store to confront employees about a sign outside the store supporting reproductive rights.
“But there’s been significantly more positive feedback from folks,” Ms. Morschauser said. “I’ve heard a lot of experiences from people who grew up here and moved away and then came back, and saw how different it has been. Things have changed.”
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