PHILADELPHIA, United States (AFP) — US presidential hopeful Kamala Harris and her freshly selected running mate Tim Walz hit the campaign trail together Tuesday for the first time, as the Democratic duo fired up supporters at a rally in key battleground Pennsylvania.

Walz, the Minnesota governor whose everyman credentials could help win over voters, joined Harris in Philadelphia to launch a tour through four swing states where the race against Republican rival Donald Trump is likely to be decided.

The latest University of Massachusetts Amherst poll has Harris leading Trump nationally by three percentage points. In the swing states Harris and ex-president Trump, who lost to President Joe Biden in 2020, are neck and neck.

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

“We fight for a future where we defend our most fundamental freedoms,” Harris told cheering supporters as Walz stood beside her.

“I set out to find a partner who can help build this brighter future. A leader who will unite our nation and move us forward. A fighter for the middle class, a patriot who believes as I do in the extraordinary promise of America.

“I’m here today because I’ve found such a leader: Governor Tim Walz.”

Expectations had always been that Harris would pick a white man to balance the ticket and help draw 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.

He dismisses the “weird” positions of Trump and Republican running mate J.D. Vance, and he is also a gun owner who tweets about hunting, goes ice fishing and rides rollercoasters with his daughter.

The one-time teacher and school sports coach flipped a Republican district in 2006 to win a US House seat from a state seen as light years from the coastal elites of California, Harris’ home turf, or the East Coast.

At the same time, Walz will appeal to the left for championing cannabis legalization, worker protections, abortion rights and tighter firearm restrictions.