The U.S. Supreme Court on Monday upheld Maryland's contested congressional map, ruling the state is allowed to count prisoners at their last known address for redistricting efforts, clearing the last legal hurdle for the redrawn districts that critics say favor Democratic lawmakers.

With the court decision, opponents have one remedy to overturn the congressional districts pushed through earlier this year by a Democratic-controlled General Assembly: another voter referendum.

Those organizing the petition drive against the congressional map must submit 55,736 signatures by Saturday to the state. If the effort makes the November ballot, it likely would join referendums on gay marriage and the state's version of the Dream Act.

Md. gay marriage opponents collect 162,000 signatures in petition drive
Those seeking to overturn gay marriage in Maryland this fall turned in their final batch of signatures against gay nuptials, collecting 162,000 in total and all but ensuring voters will decide the fate of the polarizing social issue.
The Maryland Marriage Alliance, which organized the petition drive against same-sex matrimony, had already turned in about 120,000 signatures -- more than twice the amount of names needed to start a voter referendum.
However, the group wanted to punctuate what they say is significant opposition to redefining marriage in the liberal-leaning state.
"In spite of what our opponents will say, these incredible numbers clearly show that Marylanders strongly reject the idea of redefining marriage," the group said in making the announcement.

Supporters of the recent Maryland law argued that although prisoners aren't allowed to vote, accounting for their home address -- instead of the location of their incarceration -- would provide a fairer portrait of the state's voter rolls. Noting that rural areas often house prisons, some argued that such places receive an artificial boost in voting clout at the expense of cities where the prisoners previously lived.

Another portion of the challenge to the new congressional map, claiming the redrawn districts lessened the influence of black voters, was tossed by the Supreme Court.

Some said the court's ruling strengthened the democratic process in Maryland.

"Today's Supreme Court decision affirmed the constitutional 'one person one vote' foundation of our decade-old campaign to end prison-based gerrymandering," said Peter Wagner, executive director of the Prison Policy Initiative, of the first-in-the-nation law.

Yet critics contend that political gerrymandering remains alive and well.

Maryland Republicans have called for a dramatic changing of the lines, which they say allow multiple Democratic House members to pick up support from the liberal Baltimore area. Also, Washington-area lawmakers said the new districts diluted the influence of minority voters, spreading them across a wider swath of the state and lessening their impact at the polls.

Maryland's 6th Congressional District is the most competitive race thanks to the redistricting efforts. In that contest, Democratic businessman John Delaney is challenging longtime Republican Rep. Roscoe Bartlett, whose hold on the traditionally conservative Western Maryland district is significantly at risk because of the less favorable demographics -- mainly the addition of liberal-leaning portions of Montgomery County.