Washington | Vice President Kamala Harris kicked off a critical campaign stretch aimed at putting Republican Donald Trump on the defensive in key swing states as she took the stage for the first time with her new running mate, Minnesota Governor Tim Walz.

Ms Harris personally introduced Mr Walz on stage, hailing him as a “fighter for the middle class” and touting a biography Democrats hope will broaden the ticket’s appeal to working-class voters during a rally in Philadelphia on Tuesday night (Wednesday AEST).