The president judge of Commonwealth Court, Bonnie Brigance Leadbetter, ruled that Blackwell had fallen short of the 300 voter signatures he needed to secure his spot in the Democratic primary. By Leadbetter's count, the lawmaker had only 184 valid signatures, from registered Democratic voters living inside the legislative district.

Blackwell, son of the late Democratic Congressman Lucien Blackwell and stepson of City Councilwoman Jannie Blackwell, could not be reached for comment last night. He has a right to appeal to the state Supreme Court, but a slim chance of prevailing on appeal, based on Leadbetter's evidentiary rulings.

If her decision stands, the only Democrat on the ballot will be Vanessa L. Brown, 40, a community activist who traveled to Harrisburg to file her own voter petitions last month.

She asked for copies of Blackwell's petitions on the advice of a stranger she met in the state Bureau of Elections, and when she looked through them, she saw several consecutive pages of names and addresses that appeared to be written in the same handwriting. That discovery led to her challenge of Blackwell's candidacy - and Leadbetter ultimately ruled that virtually all the signatures on those pages were invalid.

Asked last night what she intended to do next, Brown exclaimed: "Disney World." She was kidding, and quickly assumed a more politic tone. "I'm going to run a very aggressive campaign and let voters know, this is just the start of my voting for their rights," Brown said.

"We're going to do what we need to do to win this."

Brown is likely to face Republican Rahim Foreman in the general election in November.

One other Philadelphia ballot challenge is still pending in Commonwealth Court - an effort by challenger Guy D. Lewis to knock state Rep. Tony J. Payton Jr. off the ballot.

Lawrence Farnese Jr., an attorney vying for the state Senate seat now held by Vincent Fumo, survived a Commonwealth Court challenge but is still facing a Supreme Court appeal, financed by one of his opponents, electricians union leader John Dougherty. *