HARRISBURG, Pa. (AP) – Pennsylvania voters were expected to turn out in small numbers for Tuesday's primary election, with little to entice them at the top of the ticket and scattered competition for party nominations in Congress, the statewide row offices and the Legislature.

Mitt Romney, the former Massachusetts governor, has campaigned regularly in Pennsylvania even though he has had no serious opposition for the GOP presidential nomination since former Pennsylvania Sen. Rick Santorum dropped out two weeks ago. President Barack Obama is unopposed for the Democratic nod.

More than two-thirds of the state's Republican and Democratic voters were expected to avoid the polls; the forecast of rain or snow was not expected to be a significant factor.

Voters are likely to notice one change in the routine – election workers asking them for photo identification as part of a test run of the state's tough new voter ID law.

Voters will be allowed to cast ballots in the primary whether or not they have the appropriate ID. But those without it in the Nov. 6 general election would be forced to cast provisional ballots that would be counted only if the voter provides proper identification to county officials within six days.

Arguably the hottest statewide race is the two-way battle for the Democratic nomination for attorney general between Kathleen Kane, a former Lackawanna County prosecutor, and former U.S. Rep. Patrick Murphy of Bucks County.

Five men are competing for the Republican nomination to challenge Democratic U.S. Sen. Bob Casey's re-election bid: Steve Welch, a Chester County entrepreneur who is endorsed by the state GOP; Tom Smith, a wealthy former coal company owner from Armstrong County; ex-state Rep. Sam Rohrer of Berks County; suburban Harrisburg lawyer Marc Scaringi; and David Christian of Bucks County.

In another row-office contest, for the Republican nod for state auditor general, state Rep. John Maher of Allegheny County is competing against former banking lobbyist Frank Pinto.

Among the congressional primaries, several races stand out.

In the 4th Congressional District in central Pennsylvania, seven Republicans and two Democrats are vying for nominations to succeed retiring Rep. Todd Platts, a York County Republican.

In the newly created 12th District north and east of Pittsburgh, Democratic Reps. Jason Altmire and Mark Critz are competing for the nomination after the state's new redistricting law combined their previously separate districts. In the 18th District in suburban Pittsburgh, fifth-term GOP Rep. Tim Murphy faces a spirited challenge from former congressional aide Evan Feinberg.

In the 17th District in northeastern Pennsylvania, 10th-term Democratic Rep. Tim Holden faces a stiff intraparty challenge from Matthew Cartwright, a personal injury lawyer.

In the state Legislature, only four incumbent senators, out of 25 districts open this cycle, have primary opponents, while in the House only 28 incumbents could be defeated Tuesday.

Also today, voters will fill six vacant state House seats in special elections concerning one district each in Allegheny, Lehigh and Montgomery counties, and three in Philadelphia.