Sure, you can cast a provisional ballot, but will it be counted? What if you live in a different district? What if it’s a special election? The district my friend moved into had a primary for state representative decided by just 93 votes less than two years ago – which precinct you can vote in, even in the same city, can have a major effect.
Mistakes happen. So do computer glitches. Sometimes people just don’t write legibly on their registration forms, and get registered on the wrong street, or with a misspelled name. Some voters may find out the way my friend did – if they have a friend at city hall, or they’re politically active and collect signature sheets, for example. But most voters won’t find out there’s a problem with their registration until they go to the polls to vote.
Same day registration, aka election day registration, is a simple idea: If you go to your polling place and find you’re not on their list, you register to vote, right there. Your new registration takes precedence over any other registration you previously had, just as when you register at other times. A number of states, including Minnesota, Wisconsin, and next-door New Hampshire, have same day registration. They’ve been doing this for years, have found hardly any fraud with the system, and have much higher voter turnout than states without Same Day Registration.
Why don’t we have it here in Massachusetts?