The Tuesday after the first Monday in November, as mandated by law as Election day is a day in the midst of the American work week, and arises a great number of conflicts of time and interest with many citizen desiring to exercise their right to vote, but required still upon that day to work.
By making this day a Federal Holiday, a great many Citizen would be free from conflicts with work, and may exercise their right to vote without undo stress. It would further allow for a more steady progression of voters, rather than 'bottlenecks' about standard rush hour times at the polls, facilitating a better voting experience.