Continuing the uncertainty over whether Ralph Nader will be on the presidential ballot in Pennsylvania, the state Supreme Court yesterday reversed a lower court ruling that would have barred him.

In an unsigned order, the justices overturned Commonwealth Court's August decision against Nader and sent the case back to that court for an expedited hearing.

Attorneys for Nader and his challengers are now waiting for word from the intermediate court on the timing and format for further proceedings. Litigators said the most likely course would involve laborious, line-by-line review of the 52,000 petition signatures submitted by Nader in his attempt to get on the ballot as an independent.

But that will be clearer after Commonwealth Court issues a hearing schedule in response to the order and after the Supreme Court hands down an opinion explaining the reasoning behind it.

In the meantime, election preparations across the state are in limbo, as officials await the final word on whether Nader's name will be on ballots. Allegheny County, for example, has already sent out 2,700 military and overseas ballots that do not contain the independent's name.

Nader's nominating petitions were challenged by lawyers affiliated with the Democratic Party. While the submission includes more than 52,000 names, the challengers contend that at least 33,000 are invalid, meaning that Nader would fall short of the threshold of 25,697 needed to get on the ballot.

Rather than reviewing the signature issues, Commonwealth Court ruled against Nader on separate grounds. A panel of the court relied on a state statute that says no candidate can compete as an independent in the general election if he sought a political party's nomination for the office.

Because Nader accepted the nomination of the Reform Party in other states, the lower court reasoned, he forfeited his right to run as an independent in Pennsylvania. It was that finding, presumably, that prompted yesterday's high court decision, but that will be clearer after the Supreme Court files its opinion.

The renewed potential for Nader to get on the Pennsylvania ballot was one of a string of recent victories for the independent, as courts in states including Florida, New Mexico and Maryland have ruled in his favor in ballot-related cases.

In Pennsylvania as across the country, lawyers aligned with the Democrats have pushed to deny ballot access for Nader on the theory that he is more likely to siphon votes from Sen. John Kerry than President Bush. The recent Florida case was considered especially significant in the context of Bush's minuscule 574-vote margin there four years ago.

"A lot of battleground states have been putting us on the ballot," said Kevin Zeese, Nader's campaign manager. "The [Pennsylvania lower court] ruling was nonsensical."

Nader's Pennsylvania lawyer, Samuel Stretton, acknowledged that yesterday's order left significant challenges for the campaign.

He said he was scrambling to assemble a legal team that could be faced with handling multiple simultaneous hearings. Their collective results could influence not only Nader's candidacy, but, conceivably, the identity of the next president. Pennsylvania has the second-largest trove of electoral votes among the states considered up for grabs in November.

One recent survey of the state, conducted by Quinnipiac University, found Nader's support at 6 percent in a three-way trial heat in which Bush led Kerry 46 percent to 42 percent.

An ABC News poll of the state last week put Nader's support at 2 percent, with Bush leading Kerry 49 percent to 46 percent.

The state certified an official list of candidates Friday that did not contain Nader's name. Yesterday morning, just hours before the state Supreme Court ruling was announced, the county's election division mailed more that 2,700 special absentee ballots to members of the military and other overseas voters.