Aug 7 (Reuters) - Democratic contender Kamala Harris will join forces with her newly announced running mate, Tim Walz, on Wednesday for campaign events in two key battleground states, Wisconsin and Michigan, setting an early stage to showcase Walz’s Midwestern roots and political experience. The trip includes major stops in Eau Claire, Wisconsin, and Detroit, Michigan, marking Walz's first official appearances as Harris’s vice-presidential pick. Walz, Minnesota's governor, was tapped