Our Washington correspondent, Todd Zwillich, explains why Delaware, South Carolina, Pennsylvania, Wisconsin and Nevada tell the story of this election.

With so many tight political races around the country, it can be hard to determine which are the bellwethers, which ones to watch. But there are a few Senate races whose dramatic stories have resonated across the country. Their outcome will not only change the actors on the political stage, but also the narratives taking place in Washington for years to come.