Minnesota Gov. Tim Walz, the running mate for Vice President Kamala Harris, will deliver a major headline speech at the Democratic National Convention in Chicago tonight. Walz, an Army National Guard veteran and former high school teacher and championship-winning assistant football coach before he served as a congressman and governor, has been adorned with the affectionate moniker “Coach Walz” by the campaign and its surrogates. His speech in Chicago, which comes alongside other big names like former President Bill Clinton, will likely be one of the largest platforms he has had to make an impr…