WASHINGTON, United States (AFP)— Kamala Harris said Tuesday she was “proud” to tap Tim Walz as her running mate, opting for the Minnesota governor with blue-collar credentials as the partner most likely to boost her historic — and bruising — bid for the White House.

Walz had been on a vice-presidential shortlist with a string of other Democratic figures seen as broadening Harris’s appeal as she sprints into the contest against Donald Trump.

Aiming to make history as the first woman president, Harris — already a trailblazer as the first female and first Black and South Asian vice president — has little time before Election Day on November 5.

“I am proud to announce that I’ve asked @Tim_Walz to be my running mate,” she posted on X.

“As a governor, a coach, a teacher, and a veteran, he’s delivered for working families like his. It’s great to have him on the team.”

Expectations had always been that Harris would pick a white man to balance the ticket and help win over working-class, white, male voters, a demographic that propelled Trump to victory in 2016.

Walz fits that description as a 60-year-old Midwesterner with a folksy manner, decades of military experience and a rural perspective — a gun-owning Democrat who tweets about hunting.

The onetime teacher and school sports coach flipped a Republican district to win a seat in the US House of Representatives in a state seen as light years from the coastal elites of California, Harris’s home turf, or the East Coast.

At the same time, Walz will appeal to the left for championing popular Democratic policies including cannabis legalisation, increasing worker protections, safeguarding abortion rights, and supporting tighter firearm restrictions.

Trump’s campaign immediately branded the Minnesotan as a “dangerously liberal extremist” seeking to impose California values on the nation.

But “to characterise him as left is so unreal,” Nancy Pelosi, the former House speaker who worked extensively with him in Congress, told MSNBC.

Walz “is right down the middle. He’s a heartland of America Democrat.”

Walz called his naming the “honour of a lifetime” and quipped it felt like “the first day of school.”

He and Harris will hit the campaign trail immediately, launching an intense, five-day swing through battleground states starting Tuesday in the biggest prize, Pennsylvania.