"This fight isn't over," Cross said. "We won this round, but we're still going."
Should courts ultimately uphold the law, the Voter ID Coalition could continue working for a couple more years to make sure voters understand the requirement and how to comply with it, said Zack Stalberg, president and CEO of the Committee of Seventy, a Philadelphia-based group that organized the Voter ID Coalition.
But court approval is far from guaranteed. During last month's oral arguments, state Supreme Court Justice Thomas Saylor point-blank told a state lawyer that the state "can't comply with the letter of this law."
John Burkoff, a University of Pittsburgh law professor who closely follows the state Supreme Court, said the justices do not like the law as it is written.
"It doesn't take a nuclear physicist to figure that out," Burkoff said.
One major problem is the "safety net" photo ID card that the law identifies as the last resort for voters without any other valid form of photo ID. Federal Homeland Security regulations on that particular ID card make it difficult, if not outright impossible, for some people without official birth records or proof of a home address to get one.
Amending the law could provoke another high-profile debate, but it will be necessary if Republicans who control the state Legislature don't want to see the court to strike down the law, Burkoff said.
"Right now, they don't want to do that," Burkoff said. "They'd rather hope that this statute is reinstated. ... That's never going to happen."