Gov. Robert F. McDonnell called Tuesday’s ruling on the Voting Rights Act of 1965 “a potentially monumental decision” with implications for Virginia, and he called on Congress to come up with a new formula to identify which states should now be covered.

The commonwealth is one of nine states — mostly in the South with a history of discriminatory voting practices — subject to a key provision of the federal act. Under that section, states must obtain federal approval before changes are made to their voting laws.

The court’s decision means Congress must issue new guidelines to decide which jurisdictions need pre-clearance before changing laws, and it’s unclear how the ruling would affect a Virginia measure requiring voters to present photo IDs to cast ballots. The law, which McDonnell signed in March, is scheduled to take effect for the 2014 elections and was subject to pre-clearance before Tuesday’s decision.

“With Section 4 being struck, we’re in a little bit of limbo until Congress passes a new formula,” McDonnell said on WTOP’s “Ask the Governor” after the decision was announced.

“There’s nothing for us to submit to the Justice Department,” McDonnell said. “If they take six months or a year to come up with a new formula, what’s the law during that time?”

Later in the day, however, McDonnell spokesman Paul Logan clarified the governor’s remarks.

“As we review the Supreme Court’s opinion, it does not appear that the voter identification legislation will be delayed as a result of the Supreme Court’s ruling,” Logan said in a statement. “Much depends on whether or not Congress takes action to replace the stricken Section 4 of the Voting Rights Act. We will be working with the Attorney General’s Office to determine what, if any, impact the decision will have on the implementation of this legislation in July of 2014.”

McDonnell added that he will continue his efforts to expand voting rights in Virginia, citing his work on restoring felons’ rights as an example. The governor also said during the radio interview that the commonwealth has made “remarkable progress” on being more politically inclusive and is “a modern, cosmopolitan state now.”

In a statement, Attorney General Ken Cuccinelli II (R) said he would ensure that “Virginia’s voting procedures continue to comply with state and federal anti-discrimination laws.”

McDonnell is not running for reelection, and Cuccinelli is running for governor, and their potential successors also weighed in on the ruling.

“I believe that, while we have made progress, protections are still necessary to ensure that Virginians are allowed to exercise their right to vote without the risk of disenfranchisement,” Democratic gubernatorial nominee Terry McAuliffe said in a statement. “As Governor, I will work to ensure that all eligible Virginians are able to make their voices heard in our democracy.”

State Sen. Mark R. Herring (D-Loudoun), who is running for attorney general, said that the decision was “a step backward” and that the state “must remain vigilant in protecting against any effort that disenfranchises voters.” His opponent, state Sen. Mark D. Obenshain(R-Harrisonburg), author of the photo ID legislation, pledged to fight discriminatory practices regardless of the ruling.

State lawmakers looking to enact legislation similar to Obenshain’s could be emboldened by the court’s decision, said University of Richmond law professor Carl Tobias.

“Doesn’t this give them the opportunity to pass that kind of legislation without having to have it pre-cleared by Justice? I would think they would be encouraged by this,” he said.

The ruling could also make it more difficult for people to challenge laws that might affect their voting rights.

“Unless Congress acts, the real issue seems to be that the laws could go into effect and the only way to prevent that if the laws are violating voting rights is to sue over them,” Tobias said. “It’s an entirely different process.”