HARRISBURG — In Tuesday’s Pennsylvania primary, the only statewide contest is between Allegheny County Judge Jack McVay Jr. and Philadelphia Municipal Court Judge Joseph Waters Jr. for the Democratic nomination for an opening on the state Superior Court.

With most of the balloting limited to registered Democrats and Republicans, four out of five voters are expected to be doing something besides going to the polls Tuesday.

Only in unique situations, such as the special elections being held in Allegheny and York counties to fill two vacancies in the state House of Representatives, may independent voters cast ballots.

“I hate to say that, but I think 20 (percent turnout) would be good,” said Christopher Borick, a pollster and political scientist at Muhlenberg College in Allentown.

In the Superior Court race, both of the Democratic candidates and Vic Stabile, a Harrisburg lawyer who is unopposed for the Republican nomination, have received favorable recommendations from a state bar panel that reviews judicial candidates.

Waters, 60, is a retired Philadelphia police captain who put in more than 21 years on the force and will mark four years on the bench in July.

McVay, 56, a Pittsburgh resident and a licensed pharmacist, is serving his sixth year in Allegheny County’s family-court division.

The seat they are seeking was vacated last year by now-Senior Judge John Musmanno when he reached the mandatory retirement age of 70.

The 15-judge Superior Court is the state’s main intermediate appeals court. It handles a wide range of criminal and civil cases. The annual salary for a Superior Court judge is currently $188,337.