And in North Carolina, a state Barack Obama won by just 14,000 votes in 2008, keeping even a small number of voters away could make a big difference.

“The same way they’re using technology to target voters, they’re using laws to exclude voters in a targeted way,” said Bob Hall, executive director of Democracy North Carolina, a group that fought the ID law.

He said part of the rationale for having such a law “is the recognition that the election is so tight, being settled by a fraction of a percent.”

Democrats point to statements from Republicans, such as the majority leader of the Pennsylvania legislature, who said voter ID “is gonna allow Gov. Romney to win the state.”

Other GOP targets

Last year North Carolina’s Republican lawmakers considered other voting changes.

One bill would have eliminated straight-ticket voting, a method that helped Democrats in 2008. Another bill would have shortened the early-voting period. That measure passed the House, but stalled in the Senate. Early voting starts Oct. 18 this year.

In 2008 Obama won early voting in North Carolina while Republican John McCain won the Election Day vote.

Early balloting has been an issue in Ohio, where a federal judge blocked an effort to shorten the early-voting period.

According to New York University’s Brennan Center for Justice, which has fought what it considers restrictive voting laws around the country, 17 states have passed laws that could impact this year’s election. The states involved account for nearly 80 percent of the electoral votes required to win the White House.

The Center’s Diana Kasdan, said “all of these laws make a difference in one way or another.”

But whether they’ll make enough to change the presidential election is another question.

“I’m not going to say there’s no effect,” says Larry Sabato, a University of Virginia political scientist. “But unless we have another 2000 ( election which was decided by the U.S. Supreme Court), I don’t think many people will cite voter ID laws as the critical factor in selecting a president.”