 Biden won Michigan four years ago, and keeping the industrial Midwest in his column is crucial to a November victory. But Biden also has to quell a revolt among Democrats who are spooked by his debate performance two weeks ago and think maybe it's time for a younger nominee. Michigan Governor Gretchen Whitmer is often mentioned as a potential replacement. Whitmer says she still supports Biden, but she won't be at the Detroit rally because she'll be at the Sun Valley Conference in Idaho.