Who is Tim Walz? What to know about Kamala Harris' running mate

UNITED STATES - FEBRUARY 07: Gov. Tim Walz, D-Minn., prepares to testify at a House Transportation and Infrastructure Committee hearing in the Capitol Visitor Center titled "The Cost of Doing Nothing: Why Investing in Our Nation's Infrastructure Cannot Wait," on Thursday, February 7, 2019. (Photo By Tom Williams/CQ Roll Call)