Early voting tends to shift absentee and regular voters to the other available days. It doesn't have a big effect on
turnout. Changing the election day probably would be no different than early voting in terms of turnout.
I'm a little nervous about taking a fundamental right and requiring its exercise. I have a right to petition the government, but I wouldn't want to require everyone to exercise it. I have a right to bear arms, but I wouldn't require everyone to exercise it. The right to vote is a privilege, and part of that privilege is my right to not vote if I so desire.