The U.S. Supreme Court in the Crawford case held that an Indiana requirement that voters either produce photo ID, or to cast a provisional ballot and produce photo ID worthy documentation within ten days is valid, despite a complete lack of evidence that imposters showing up to vote is a genuine problem in the state. Photo IDs are free in Indiana (escaping the issue of a direct poll tax), but obtaining documentation to get a photo ID or to support a provisional ballot is not, nor are in person trips to the pertinent government offices which are difficult for people who generally do not have cars and often do not have access to public transportation.
The state conceded that as many as 1% of voters in the state (mostly elderly, poor, minority and disabled) would be affected by the law. The Democratic Party of Indiana claimed that more were impacted. The dissenting opinion noted that the Democratic Party had identified more than twenty people in a single Indiana precinct who cast provisional ballots and were likely eligible voters (due to signature matches with registration documents and a prior history of voting, for example) whose provisional ballots were not counted as a result of the photo ID requirement. There are thousands, if not tens of thousands, of precincts in Indiana.
The dissenting opinion by Justice Souter noted that there is no evidence that anyone has ever impersonated a voter in Indiana at the polls and also suggested why this might be the case. The leading opinion from Justice Stevens identified only one such proven case in the entire nation in recent history (in Washington State), and a corruption situation in New York State from 140 years ago.
Thus, the State of Indiana won this case on the law, in a divided opinion, but the facts revealed in the process make clear that this law disenfranchises many more people who have a right to vote than it prevents from casting ballots improperly. It also, once again, makes the U.S. Supreme Court look like it is acting in a partisan manner to disenfranchise voters in close elections, just as it did in the imfamous 2000 case of Bush v. Gore.
Still, from a practical perspective, the impact is not earth shaking. The percentage of people who lack photo IDs by the highest measure does not exceed 6%-10% of the population and may be 1% or lower. Voter turnout in the population of eligible voters without photo IDs has always been exceedingly low compared to other demographics, for the same kinds of reasons that make it hard for this population to obtain photo IDs.
To the extent that the barriers to obtaining photo IDs are primarily economic, the amount of money a non-profit would have to secure in Indiana to overcome these barriers is on the same order of magnitude as the value of the goods and services involved in taking a case all the way to the U.S. Supreme Court. A few hundred thousand dollars would be sufficient given the number of people impacted who really want to vote and the costs involved to help most people who are not voting due to economic barriers associated with photo ID requirements. Campaign technology is sophisticated enough that it is possible to be efficient about it by using techniques like targeting for assistance people who cast provisional ballots but did not validate them, and registered voters who didn't vote in counties where there were many provisional ballots cast but not validated.
Such a campaign would produce benefits to Democrats at the ballot box year after year, and unlike voter registration campaigns, which are already common, a photoID campaign would also help people without photo IDs clear other hurdles in life, such as obtaining government benefits and dealing with encounters with police.
Yes, this decision clearly helps Republicans in a razor thin election with high turnout in a Presidential election year (when marginal voters most often vote), and it is not inconceivable that Indiana could be a swing state in a statewide race in such a year. But, no Democrat with a two percentage point lead in any statewide race and a viable campaign war chest has much to fear from it, and the areas where the highest concentrations of disenfranchised voters live are likely to be the safest districts for Democrats at a less than statewide level.