Trump continues to lead in several polls of battleground states, but Ms Harris hopes Mr Walz will bolster her support in the critical “blue wall” states of Michigan and Wisconsin.
The Trump campaign has targeted the Rust Belt and had even focused on Mr Walz’s home state of Minnesota, once considered a reliably blue bastion in the Midwest.
The selection of Mr Walz, a plain-speaking, denim-wearing bespectacled white man, is an acknowledgment the Democrats need to win back blue collar voters in the American heartlands.
Critical battleground states
Mr Walz’s experience both as governor and as a former Congressman, as well as his personal rapport with Ms Harris, were also critical to his selection, White House insiders said.
Joe Biden said the pair were “a powerful voice for working people and America’s great middle class”.
They will spend the next five days touring critical battleground states, visiting Eau Claire, Wisconsin, and Detroit on Wednesday and Phoenix and Las Vegas later in the week.