In November, I had to vote by provisional ballot. Happens to a lot of people, often for no good reason. But if I had stayed closer to home instead of moving across the state line, along with making my parents happy I likely would have avoided this frustrating experience at the polls. Wisconsin doesn't use provisional ballots on anything like the level that Illinois does, because Wisconsin allows election-day voter registration.
Election-day registration leads to high voter turnout and low incidence of registration problems and the like. These factors helped Wisconsin perform first among the states in Pew's Election Performance Index, which came out last month. It's cost-effective, too: the State's Government Accountability Board recently found that eliminating election-day registration would cost at least $5 million (pdf, via Brenden Timpe).
When officials attack a policy that boosts voter turnout, saves money, and doesn't seem to cause any actual problems, it's hard to conclude that their goal is anything other than vote suppression itself. And vote suppression is quite literally an attack on democracy.
The good news is that election-day registration appears to be safe for now in Wisconsin and a few other states—and several others are considering adding this pro-democracy policy.