The polling average in 21 states has shifted toward Donald Trump in the past month, according to modeling by analyst Nate Silver. According to Silver's model, last updated on Sunday, Kamala Harris still leads nationally and in three key swing states of Michigan, Wisconsin, and Nevada, the candidates are tied in Pennsylvania, and Trump leads in Arizona, Georgia, and North Carolina. But compared to the same model's aggregate polling from one month ago, almost every state tracked has shifted slightly toward Trump, including nationally and in all seven battleground states. The biggest swing in a battleground state, was in Michigan,...