With her choice of a Midwestern governor as a running mate, Vice President Kamala Harris pushed to shore up "Blue Wall" states -- Wisconsin, Michigan and Pennsylvania -- that Democrats need to win to keep the White House. Harris, the Democratic presidential nominee, had already signaled that she would also contend in Sun Belt states that increasingly seemed out of reach for President Joe Biden.

Harris, the first Black woman and woman of South Asian descent to head a major party ticket, and former President Donald Trump, the Republican nominee, will also be locked in Sun Belt competition to win Georgia, Arizona, Nevada and North Carolina, an electoral map that has expanded since Biden's decision to withdraw from the race.

Her ascension and the enthusiasm it generated across racial and generational lines forced mapmakers in both parties to redraw the battle lines of the campaign, Republicans and Democrats agree. Biden's difficulties -- especially among younger voters and nonwhite voters in the Sun Belt -- had required him to win all three Blue Wall states and hold off Trump in Democratic-leaning Minnesota to have a chance at an Electoral College majority.

"Black women candidates have a unique ability to build multiracial coalitions," said Democratic campaign strategist Lauren Groh-Wargo, who managed Stacey Abrams' two campaigns for Georgia governor. "That's the opportunity Kamala presents especially in the South and the Sun Belt, which have the most racially and ethnically diverse states of the battlegrounds."

Chuck Coughlin, a longtime Republican consultant in Arizona, said the switch from Biden to Harris was a jolt in his state and beyond: "Once he stepped aside it was as if you released a torrent of energy."

The vice president, a California native whom Republicans lambaste as a "San Francisco liberal," on Tuesday unveiled Minnesota Gov. Tim Walz as her running mate. A 60-year-old Army National Guard veteran, public school teacher and former high school football coach who once represented a wide swath of rural and small-town Minnesota in Congress, Walz adds a distinctive Rust Belt brand to the Democratic ticket.

"Tim Walz can play well in the parts of Pennsylvania and other Rust Belt states where Joe Biden was stronger than Democrats sometimes are," said Mike Mikus, a veteran of Democratic campaigns who is based in Pittsburgh. "And Kamala Harris is really well positioned for the suburbs and into the cities."

The immediate reaction from Trump's campaign suggests they won't alter the arguments they were making before Harris tapped Walz.

"It's no surprise that San Francisco Liberal Kamala Harris wants West Coast wannabe Tim Walz as her running-mate. Walz has spent his governorship trying to reshape Minnesota in the image of the Golden State," said Karoline Leavitt, a spokeswoman for the former president.

Trump narrowly won the Blue Wall states in his 2016 race against Hillary Clinton only to lose them four years later to Biden, who also added Georgia and Arizona to his winning coalition.

After Biden's disastrous debate performance in June, the 81-year-old's options winnowed, and Trump was poised to capitalize across the electoral map. The former president emerged even stronger when he survived an assassination attempt two days before the Republican National Convention. Trump selected Ohio Sen. JD Vance, another conservative populist, as his running mate in an effort to lock down working-class voters.

It was a "movement pick" made out of confidence, Trump ally and former House Speaker Newt Gingrich said at the time. Republicans came out of their convention in Milwaukee talking not just about an Electoral College victory in the presidential race but a landslide that would usher in House and Senate majorities and domination of statehouses around the country. And in Vance, Gingrich said, Trump was not simply adding a running mate, he was anointing a successor.

Then, Biden dropped out and endorsed Harris, and within a matter of days she had raised $200 million, attracted tens of thousands of new volunteers and secured commitments from enough Democratic delegates to make her the eventual nominee - the position she officially earned Monday night.

While a national campaign turns on issues that resonate with voters across state and regional boundaries, there are key differences in the two presidential campaign fronts.

The upper Midwestern states and Pennsylvania, in general, have slightly older, whiter electorates, and a higher percentage of the population is native-born to the states where they still reside. For example: The Census Bureau measured the U.S. population to be 58.4% non-Hispanic white in 2023, while Michigan, Pennsylvania and Wisconsin all exceeded 73%. Arizona was 53.4% while Georgia was 49.6% .

Arizona, meanwhile, is just a tick above the nation's median age of 38.9, and Georgia's median is more than a full-year younger. The three Blue Wall states all have medians above 40, highlighting younger voters' strength in closely divided Sun Belt states.

Reflecting the Rust Belt's industrial history, labor unions, especially private sector unions, are stronger than in both the southeastern and southwestern Sun Belt - with the notable exception of Las Vegas, where unions of the casino and tourism sectors are major political forces.

The Sun Belt states have been faster growing than the Great Lakes region for decades and, on average, have younger electorates. Business booms and retirement options have drawn newcomers to metro areas like Phoenix, Las Vegas, Atlanta, Charlotte and the "Research Triangle" that comprises Raleigh, Durham and Chapel Hill in North Carolina. They also have larger Hispanic populations.

North Carolina and Georgia have large Black populations, which, like Hispanic populations in the southwest, include voters with generational ties to the region and more recent arrivals.

The largest metro areas in Georgia and North Carolina also boast fast-growing Asian American populations.

The deeply rooted segments of the nonwhite populations also mean that the Sun Belt states have a more racially and ethnically diverse rural and small-town population. That's different from the Rust Belt states, where more of the nonwhite population is concentrated in metro areas.

Harris' deliberations on a running mate seemed to reflect a keen awareness of the two broad fronts of the battleground map. Her other finalists included Pennsylvania Gov. Josh Shapiro, who won a landslide in 2022, with especially strong support from the Philadelphia suburbs, and Arizona Sen. Mark Kelly, a Democrat who has sometimes been critical of the Biden administration's handling of border and immigration policy.

But Mikus, the Pennsylvania Democrat, said Harris ultimately found the right choice for a ticket the reflects the breadth of her ideal coalition.

"The ticket as a whole is mostly above brand and vibe," he said. "They've got a good combination there."

But for Groh-Wargo, it starts with the presidential nominee and, in this case, what Harris means in states that Biden would have had difficulty winning.

"People talk a lot about the challenges that Black candidates and women candidates have," Groh-Wargo said, "but I don't think we talk enough about the opportunities."

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Associated Press reporter Jonathan J. Cooper contributed from Washington.