In advance of Monday's trial over Pennsylvania's voter identification law, opponents of the measure rallied in Harrisburg.

The full panoply of liberal political interests filled the Capitol rotunda as roughly 150 people turned out Thursday. Union members, environmental advocates, and civil rights activists protested Pennsylvania's law requiring people to have certain state-issued IDs to cast ballots.

NAACP national president Ben Jealous calls Pennsylvania "ground zero for the fight for voting rights in the North."

"We need everyone who can be at the courthouse on Monday to be there," he said. "This judge needs to see, the state needs to see, our nation needs to see, just how important this trial is."

The upcoming trial will decide if Pennsylvania's voter ID law is constitutional.

Supporters say the measure combats voter fraud, but opponents say it will disenfranchise those voters who have difficulty getting the required ID.

"It's a ploy to take votes away from people who deserve them -- veterans, seniors, students, people with disabilities, people of color, and hard-working folk," said John Jordan of the NAACP.

Past court rulings were temporary -- blocking the law's enforcement in the 2012 general election and this year's primary.

The ruling is expected to be appealed to the state Supreme Court.