There is very little evidence that the integrity of the ballot box is endangered. A Rutgers U professor, as well as several NGOs, have studied voter fraud, and concluded that the occurrences of the kind of fraud that voter ID would prohibit are statistically negligible. In addition, voter ID laws make it more difficult and expensive for people to vote. Government IDs can be expensive and time-consuming to procure (depending on one's state) - and a bar for people who move frequently and have small incomes. US elections already suffer from low voter turnout - we should be encouraging more participation, not discouraging the turnout we already have. The resources wasted on searching for voter fraud would be far better spent on opening more voting places, and targeting the kind of fake Facebook news that too many people consume. As fewer people vote, government loses its democratic legitimacy. 

Finally, Colorado's mail ballots are a great thing.