Ada County is getting redder and redder. See how your neighborhood has changed

Idaho Democrats were proud to field candidates in every legislative race this election. They outraised the Republican Party by a wide margin and drew $70,000 from the Democratic National Committee to invest in minority voter turnout, the Idaho Statesman previously reported.

But they faced resounding defeats across the state and losses in Ada County. In West Boise’s purple legislative District 15, Democratic incumbent Sen. Rick Just lost to Republican challenger Codi Galloway, while Republican Rep. Dori Healey fended off a challenge from Democrat Shari Baber. Republican incumbents won all county races handily — in commissioners’ races, by their widest margin since at least 2016.

In part, the shift to the right mirrors the area’s changing political demographics. Between 2004 and 2023, nearly 120,000 people originally from other states registered to vote in Idaho, according to the Idaho Secretary of State’s Office, which tracks voter registrations. Amid the state’s population boom, Republican newcomers vastly outnumber Democratic voters. Except for Vermont, every state in the U.S. has sent more Republicans than Democrats to Idaho, according to the state data.

Many newcomers are politically active and enthusiastic, said Thad Butterworth, chair of Ada County’s Republican Party.

There’s “a very large contingent of people who are coming from some of these states where they felt like they were not listened to by their by their government, by their party,” Butterworth told the Statesman by phone. “The new contingent, they want action. They want to see things moving. They want they want to be able to look at the end of the day and say, ‘We moved the ball forward.’”

Statewide, about a quarter of those newcomers are from California. Secretary of State voter registration data shows that more Californians moved to Ada County than anywhere else in Idaho.

The changes reflect a national trend: Millions of Americans have moved along political lines in recent years, resulting in a “widening gap” between blue and red neighborhoods, the New York Times reported in October.

Ada County’s population has grown dramatically: from about 200,000 residents in 1990 to over 550,000 in 2024, according to data from the Community Planning Association of Southwest Idaho. More than 60% of Idaho’s new registered voters are over 50, according to Secretary of State data.

We mapped the county’s voting patterns in every presidential election, by precinct, since 2012. The redder a precinct is, the more votes cast there for the Republican candidate. The bluer it is, the fewer votes cast for a Republican.

The data shows that political polarization is occurring below the state level, too — as some formerly pale-red and light-blue neighborhoods turn maroon and darker blue.

Both southern and northwestern Ada County have grown redder since Donald Trump’s first run for the presidency in 2016. In the county’s largest precinct, on its southern border, Trump received about 65% of the vote in 2016 — and nearly 75% of the vote in 2024.

In the northwest, around Eagle and Star, Trump earned about 63% of the vote in 2016 and over 80% in 2024.

Democratic support has remained strongest in central Boise and in the North and East Ends, where the Democratic candidate has regularly received over 50% of the vote since at least Barack Obama’s 2012 campaign.

Support for Democrats was highest in the North End in 2020, with Joe Biden hitting a high of nearly 88%. Support flagged for Kamala Harris in the same area, receiving nearly 83% this year.

Voters between Meridian and Boise have consistently been the most split between Democratic and Republican presidents. In one neighborhood near Summerwind Elementary School, residents in 2020 voted for Trump by a 0.11% margin.

The maps below show each Ada County precinct’s voting patterns since 2012. Note: Precincts’ boundary lines have shifted multiple times since 2012 as the region has grown, which could partly explain differences in each precinct’s voting patterns.

This story was originally published November 9, 2024 at 4:00 AM.

Nick Rosenberger

Idaho Statesman

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Nick Rosenberger is the Idaho Statesman’s growth and development reporter who focuses on all things housing and business. Nick’s work has appeared in dozens of newspapers and magazines across the Pacific Northwest. Support my work with a digital subscription

Sarah Cutler

Idaho Statesman

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Sarah covers the legislative session and state government with an interest in political polarization, government accountability and the intersection of religion and politics. Please reach out with feedback, tips or ideas. If you like seeing stories like hers, please consider supporting her work with a digital subscription. Support my work with a digital subscription