HARRISBURG — Competition for a solitary opening on the Pennsylvania Supreme Court could be fierce, with multiple candidates jockeying for Democratic and Republican party endorsements in the May primary election.

At least four Republican judges are planning to run for the seat or seriously considering it — Superior Court judges Joan Orie Melvin, Cheryl Allen and Jacqueline Shogan, and Philadelphia Common Pleas Judge Paul Panepinto — in an election year that state GOP leaders hope will be a watershed for their ailing party.

Two Democratic candidates have emerged so far — Superior Court Judge Jack Panella and Philadelphia Common Pleas Judge M. Teresa Sarmina, a newcomer to statewide politics.

A one-seat majority on the state's highest court flipped from Republican to Democratic in 2007, when voters filled two open seats.

This year's race to succeed Justice Jane Cutler Greenspan, a Democrat, will either preserve the Democrats' majority or restore GOP control. The outcome could take on unusual importance in the likely event that the Supreme Court is pulled into the politically charged redrawing of legislative district boundaries based on the 2010 census.

"This is big, because theoretically (the balance) is tied," state Republican Party Chairman Rob Gleason, referring to the vacancy left by the retirement of former Chief Justice Ralph Cappy a year ago. Greenspan was appointed to finish Cappy's term on the condition that she not seek election to a full 10-year term.