The Supreme Court on Wednesday upheld Pennsylvania's newly drawn congressional boundaries, but left the door open to future challenges claiming party politics overly influenced election maps.

The court voted 5-4 in favor of the boundaries drawn by the Republican-controlled Legislature. State Democrats had challenged the map as being too friendly to GOP candidates.

Four court conservatives would have gone even further, by limiting future legal attacks on gerrymandering, the practice of drawing voting districts to favor a political party.

Those justices — Chief Justice William H. Rehnquist (search), Sandra Day O'Connor (search), Antonin Scalia (search) and Clarence Thomas (search) — wanted to overrule a 1986 high court ruling that permitted challenges. A fifth moderate conservative, Justice Anthony M. Kennedy (search), disagreed, as did four liberal justices.

Kennedy voted with the conservatives in upholding Pennsylvania's new map.

States must redraw boundaries every 10 years to reflect population shifts. Pennsylvania lost two congressional districts after the 2000 census and Democrats and Republicans battled extensively over a new 19-district map.

Republicans hold 12 of Pennsylvania's 19 House seats, even though Democrats have the edge in registered voters. When the state had 21 seats, Republicans held an 11-10 advantage.

Democrats had charged that political gerrymandering violates the "one-person, one-vote" requirement protected in the Constitution.

While the Supreme Court has made it almost impossible to win a claim that partisan gerrymandering is unconstitutional, justices left the door open to such claims in the splintered 1986 ruling at issue Wednesday.

Scalia, writing the court's main decision, said that courts have wrangled for 18 years over the subject "with virtually nothing to show for it ... we must conclude that political gerrymandering claims are nonjusticiable and that (the ruling) was wrongly decided."

Kennedy, in his separate opinion, said that "a decision ordering the correction of all election district lines drawn for partisan reasons would commit federal and state courts to unprecedented intervention in the American political process." He added, however, that courts must be open to the possibility of unconstitutional line-drawing.

Stevens, Souter and Breyer each wrote their own opinions as well, expressing reservations about closing courts to some fights over redistricting.

Scalia said that politics in boundary-drawing dates back to the beginning of the 18th century in Pennsylvania, in a dispute over the political power of the city of Philadelphia.

"It was generally conceded that each party would attempt to gain power which was not proportionate to its numerical strength," Scalia wrote.

The case is Vieth v. Jubelirer, 02-1580.