He added: "Protecting the right to vote, ensuring meaningful access, and combating discrimination must be viewed not only as a legal issue but as a moral imperative. And ensuring that every eligible citizen has the right to vote must become our common cause."
Holder's comments come nearly four weeks after the Justice Department's Civil Rights Division ruled that South Carolina's voter identification law was discriminatory because it would make voting more difficult for minorities, who lack sufficient forms of government-approved ID more often than whites do.
Justice officials weighed in on the law under Section 5 of the 1965 Voting Rights Act, which requires approval of proposed voting-law changes in 16 mostly Southern states that have histories of discrimination.
"We'll also continue to review other types of changes to our election systems and processes - including to the procedures governing third-party voter registration organizations, to early voting procedures, and to photo identification requirements - to ensure that there is no discriminatory purpose or effect," Holder said.
South Carolina is one of 13 mostly Republican-controlled states that have approved new voting laws that include requiring government-approved photo ID to register or vote, shortening early voting periods, and curtailing registration efforts by third-party groups such as the League of Women Voters or the NAACP.
Supporters of the new laws say they're needed to protect against voter fraud. Several studies and investigations - including a five-year probe by President George W. Bush's Justice Department - indicate that voter fraud in the United States is negligible, however.
Opponents view the new laws as a thinly veiled effort to suppress the votes of minorities, the elderly and the young - key voting blocs for the Democratic Party.
An October study by New York University's Brennan Center for Justice estimated that the new laws would hurt more than five million voters nationwide, mostly minorities who lack sufficient government-sanctioned photo IDs or the materials to obtain the IDs.
Most of the Republican presidential contenders have derided the Justice ruling on South Carolina's voter law as unwarranted federal meddling. South Carolinians vote Saturday in the GOP presidential primary.
Former House Speaker Newt Gingrich, former Pennsylvania Sen. Rick Santorum, and Texas Gov. Rick Perry have accused the Obama administration of turning a blind eye to voter fraud and have accused President Obama's reelection campaign of trying to steal the 2012 election.