Concerned that voting machine breakdowns could cause long lines on Election Day, particularly in minority neighborhoods, several groups filed a lawsuit on Thursday to force Pennsylvania election officials to provide paper ballots when half the machines in a precinct have failed.

The top election official, Secretary of the Commonwealth Pedro A. Cortés, has directed poll workers to provide paper ballots to a precinct only when all of its touch-screen voting machines are broken.

The lawsuit was filed in Philadelphia by the Pennsylvania N.A.A.C.P.; the Election Reform Network, a nonpartisan group; and a coalition of individual voters. It asks a federal judge to declare Mr. Cortés’s directive unconstitutional on the grounds that it puts an undue burden on residents who may have to wait hours to vote.

Mr. Cortés said that current safeguards should ensure an efficient election and that forcing a change could confuse poll workers who had already been trained.