Common Cause helped bring down Pennsylvania's old congressional district map. Now, in a twist, the good-government group might undo the new map that replaced it.

Micah Sims, executive director of Common Cause Pennsylvania, said his organization and the state NAACP are considering filing suit in federal court to challenge the new map imposed by the Pennsylvania Supreme Court this week.

He said it may violate the 1965 Voting Rights Act, which banned obstacles to voting by minorities.

Under Pennsylvania's former 2011 map, drawn by Republicans, nonwhites make up a majority of residents in two Philadelphia-based congressional districts. In the new map, people of color appear to be the majority in only one district, he said.

"In general, I think the new map is a really big win for democracy in Pennsylvania," Sims said. "However, we want to make sure that it is not disenfranchising voters, particularly in Philadelphia."

Common Cause has recruited several of the plaintiffs for the lawsuit that led to the 2011 map's being struck down by the Pennsylvania Supreme Court as unconstitutionally gerrymandered. It also is a leader in the Fair Districts PA coalition.

The NAACP Pennsylvania State Conference, too, has argued that the gerrymandered 2011 map amounted to "voter suppression." This week, it submitted the new map to the national association's legal team to determine whether it complies with the Voting Rights Act.

Minister Rodney Muhammad, president of the Philadelphia NAACP, said the new one splits up communities of color.

"They're broken apart and minimized in a way that they could never hope to make meaningful change," he said. "This disengages and disempowers people. And, frankly, all of the apathy that we've had to fight against? This only reinforces it."

Sims stressed that the two groups were still examining data to determine the exact demographic makeup of each congressional district.

"We are not moving hastily," he said, adding that the "last thing" the groups want to do is "disrupt democracy."

If the organizations file a lawsuit, they will join several others in challenging the map. Pennsylvania  and national Republicans said they will sue to block the map, arguing the state Supreme Court violated the U.S. Constitution by taking power from the legislature.

Citing the issues raised by Common Cause, Republican U.S. Rep. Ryan Costello called the map "racist." He noted that State Sen. Vincent Hughes, an African American Democrat, urged Gov. Wolf to retain two majority-minority districts in the city.

"It didn't happen because the Supreme Court looked to partisan gerrymander and they ignored the Voting Rights Act and in the process they disenfranchised African American voters," Costello said.

A challenge to the map under the Voting Rights Act would require substantial evidence beyond simple demographics, said Michael McDonald, a political science professor at the University of Florida who has served as an expert witness or consultant in multiple redistricting and election lawsuits.

If there is a significant minority community in a geographic area, the Voting Rights Act does not require that the congressional district be drawn to be majority-minority, McDonald said. The law requires that the minority be able to effectively elect the candidate of its choosing.

"It's going to be difficult to mount the evidence," McDonald said. "If the evidence is going to fall back to, 'The district was reduced in African American population,' that's not sufficient. You've got to establish that the African American community is not effective in electing its candidate of choice."

That can be complicated, he said. For one thing, the minority community's preferred candidate can be white, or of another racial or ethnic group.

Or multiple minority groups can form a de facto coalition to elect a candidate even if no group makes up a majority.

Or, McDonald said, enough white voters in a majority-white district can side with minority voters to elect their preferred candidate.

Making a case in Philadelphia is further complicated in that only one of the three current U.S. representatives with city-centered districts is black. Rep Bob Brady's First Congressional District, which stretched from portions of South Philly to parts of Delaware County under the previous map, is majority-minority, but Brady is white.

So if the argument is that Philadelphia has gone from two majority-minority districts to only one, McDonald said, the question becomes: Why wasn't this a problem under the previous map? Was Brady not the preferred candidate for the minority groups in his district?

Plus, McDonald noted, the court map was drawn by Stanford University law professor Nathaniel Persily, who has helped courts produce maps in multiple states and is widely regarded as fair and expert.

"He understands the Voting Rights Act. He wouldn't draw a district that he thought wasn't going to be effective for voting rights, so he'd be careful about that," McDonald said. "It's a detail that would not escape him."