Much has changed since late January 2016, when the presidential candidates of both parties were on the eve of the Iowa Caucuses. Nominees and running mates have been chosen. Conventions have come and gone. Scandals have dominated the headlines only to be forgotten a few days later when something new and even more outrageous takes their place.

But one fascinating poll number has stayed in place for quite some time: The percent of Americans who say they would be anxious about one or both candidates becoming president. And it’s this very metric – which candidate makes swing voters more nervous – that may be critical.