When I left for North Carolina last week to canvass for Hillary Clinton, I knew exactly why I was going. As a former field organizer, I know the impact door-to-door canvassing can have on an election. In 2008, when President Obama won North Carolina, the margin of victory was 14,177 votes. That was the closest margin in any state in the country. I went to North Carolina because I knew the doors I knocked on would make a difference in one of the tightest races in the country.