More than a dozen states have passed such laws. Democrats say it will discourage eligible voters.
Since Republicans won control of many statehouses last November, more than a dozen states have passed laws requiring voters to show photo ID at polls, cutting back early voting periods or imposing new restrictions on voter registration drives.
With a presidential campaign swinging into high gear, the question being asked is how much of an effect all of these new laws will have on the election races. State officials, political parties and voting experts have all said it could be sizable. Now, a new study to be released Monday by the Brennan Center for Justice at New York University School of Law has tried to tally just how many voters stand to be affected.
The center, which has studied the new laws and opposed some of them in court, analyzed 19 new laws and two executive orders in 14 states, and concluded that they "could make it significantly harder for more than 5 million eligible voters to cast ballots in 2012."
Republicans, who have passed almost all of the new election laws, say they are necessary to prevent voter fraud. Democrats counter that the new laws are a solution in search of a problem, since voter fraud is rare. They worry that the laws will discourage, or even block, eligible voters -- especially poor voters, young voters and black voters, who tend to vote for Democrats.
In late May, Minnesota DFL Gov. Mark Dayton vetoed a GOP bill that would have required photo ID at the polls, saying that election-law measures should reflect a broad bipartisan consensus.
The Justice Department must review the new laws in several states to make sure that they do not run afoul of the Voting Rights Act. The Supreme Court upheld Indiana's voter ID law in 2008, saying that while it found no evidence of the fraud the law was intended to combat, it also found no evidence that the new requirements were a burden on voters.
"This year there's been a significant wave of new laws in states across the country that have the effect of cracking down on voting rights," said Michael Waldman, the Brennan Center's executive director, who noted that 5 million votes would have made a difference in both the 2000 and 2004 presidential elections. "It is the most significant rollback in voting rights in decades."
Just how much of an effect the new laws will have is a matter of some dispute. Sen. Dick Durbin, D-Ill., who held a hearing on the new laws last month, said they "will make it harder for millions of disabled, young, minority, rural, elderly, homeless and low income Americans to vote."
Republicans note that such states as Georgia and Indiana moved to require photo ID from voters and that turnout there improved.
Some of the new laws have been introduced by Republicans for years, but passed only this year after the party made so many gains at the state level. Others have been promoted vigorously by conservative groups. But there is little doubt that they will alter the voting landscape.
Five states passed laws this year scaling back programs allowing voters to cast their ballots before Election Day, the Brennan Center found.
Ohio passed a law eliminating early voting on Sundays, and Florida eliminated it on the Sunday before Election Day -- days when some African-American churches organized "souls to the polls" drives for congregants.
Maine voted to stop allowing people to register to vote on Election Day -- a practice that had been credited with enrolling some 60,000 new voters in 2008. Voters in Maine and Ohio are now seeking to overturn the new laws with referendums.
The biggest effect, the Brennan Center said, will be from laws requiring people to show government-issued photo ID to vote. This year, 34 states introduced legislation to require it -- a flurry of activity that Jennie Bowser, a senior fellow at the National Conference of State Legislatures, called "pretty unusual."
Before this year, only two states, Indiana and Georgia, had "strict" photo identification requirements for voters. This year, five more states -- Wisconsin, Kansas, South Carolina, Tennessee and Texas -- passed laws to join their ranks. Under the Texas law, licenses to carry concealed handguns would be an acceptable form of identification to vote, but not student ID cards.
The Brennan Center estimates that 11 percent of potential voters do not have state-issued photo ID. By that measure, it finds that the new laws would affect 3.2 million voters in the states where the change is scheduled to take effect before the 2012 elections.
While other groups have made similar estimates in the past, Hans von Spakovsky, a senior legal fellow at the Heritage Foundation, argued that the number is too high. But there is little dispute the new laws will have an effect on a large number of voters.
South Carolina and Texas estimate that between them they have more than 800,000 registered voters who may not have acceptable forms of photo ID. While both states would offer free identification cards that would be acceptable at the polls, critics of the new laws worry that the added barrier to voting could discourage people from going to the polls. South Carolina estimates that 8 percent of its voters -- 216,596 people -- do not currently have the proper identification.
Texas calculated that at least 95 percent of its registered voters have a driver's license or valid ID card, but could not say for sure whether the 605,576 names on its voter list that do not appear on its lists of people with driver's licenses or state-issued ID cards have them or not.