The Justice Department’s decision last week to block a new South Carolina law requiring voters to present photo identification is only the first of what will be a year-long battle between advocates and opponents of stricter voting laws. And the results of those fights could determine the winner of the 2012 presidential election.

South Carolina Gov. Nikki Haley, a Republican, said her state will appeal DOJ’s decision in court, casting it as “bullyingsimilar”>by the federal government. At the same time, civil right groups are promising to fight provisions in states such as Wisconsin and Texas, arguing these laws unfairly target minorities, who are less likely to hold photo identification.

The law passed earlier this year in Wisconsin, which goes into effect in 2012 and would require a photo ID to vote, is particularly important. President Obama easily won the Badger State in 2008, but it has shifted sharply to the right since then; Republicans won the U.S. Senate seat and governor’s race last year. Texas is a traditionally-Republican state, but Obama campaign officials say the state’s growing popular of voters under 40 and Latinos could allow them to compete there.

The American Civil Liberties Union filed a lawsuit seeking to strike down the Wisconsin law earlier this month, and the group is encouraging DOJ to block the Texas law as well. (Attorney General Eric Holder has said his department is scrutinizing the Texas law closely) The ACLU lawsuit will be an uphill climb; in 2008 the U.S Supreme Court upheld a similar law in Indiana.

“The (Justice) Department affirmed that federal law cannot tolerate election statutes that make it harder for minority citizens to vote,” said Michael Waldman of the Brennan Center’s for Justice, a New York-based liberal leaning group that has targeted the voting laws. “Now the Department should subject other state laws to similar scrutiny.”

Under the Voting Rights Act, states and localities that in the past limited voting rights of certain parts of the electorate must get changes to their voting laws pre-approved by the Department of Justice. The states that fall under this provision include Alabama, Alaska, Arizona, Georgia, Louisiana, Mississippi, South Carolina and Texas.

The rejection of South Carolina’s law, while hailed by civil rights groups, may have little electoral impact, as Obama is very unpopular in South Carolina and had virtually no chance of winning the state. Most of the southern states that must get pre-clearance for their changes are similarly Republican-leaning.

But the Justice Department’s investigation into South Carolina shows the impact these provisions might have in a more competitive state like Wisconsin. In a letter to South Carolina officials, Thomas Perez, head of the Civil Rights Division at the Justice Department, estimated 239,000 voters in the state were registered but did not have photo identification and would be ineligible to cast ballots unless they obtained a driver’s license or another form of identification.

That number of voters, while small, could be determinative. In 2008, Obama won Indiana by 26,163 votes and lost Missouri by 3,632.

For Obama, the laws are a complicated political challenge. Since 2008, a series of measures, advanced by Republican-controlled state legislatures, have been passed that could limit participation by the so-called Obama coalition: blacks, Hispanics and young voters. Some of the laws, such as the one in Texas, would make it harder for college students to vote if they only have student identification, while the voter id laws are expected to impact blacks and Latinos.

The Brennan Center estimates up to five million people across the country would be affected by the provisions.

Leading African-American officials in Washington, such as Rep. John Lewis, have attacked these provisions as attempts to suppress the vote. But the idea that photo identification should be required for someone to vote is popular, even passing earlier this year in the liberal state of Rhode Island.

“Until people realize the effects of these laws, they are going to this it’s a great idea,” said Rep. Marcia L. Fudge, who represents a district in the Cleveland area.

Politically, Obama may be forced to signal support or ambivalence for these measures, even if his own Justice Department is trying to get them.