By Joseph Ax
NORRISTOWN, Pa. (Reuters) - Public transportation workers in Philadelphia went on strike on Tuesday, leaving thousands of residents in the fifth largest U.S. city scrambling to find transportation options and raising concerns that a prolonged work stoppage could hamper residents from voting in next week's presidential election.
Some 4,700 workers represented by the Transport Workers Union Local 234 went on strike after they were unable to reach a contract agreement with Southeastern Pennsylvania Transportation Authority (SEPTA), a system that provides almost 1 million rides a day.
The strike shut down bus and most trolley routes in Philadelphia. SEPTA told its riders to use its regional rail service as an alternative and to expect significant delays and crowding.
The evening rush hour was further disrupted as picketers blocked regional rail crews from getting to their trains, though SEPTA said on Twitter that employees were able to access trains after a delay.
City officials expressed concern that the strike could cause trouble for voters trying to get to polls next Tuesday.
In a statement, SEPTA said it was hopeful that an agreement could be reached prior to Election Day but added that it was prepared to seek an emergency court order requiring employees to work that day.
Registered Democrats outnumber Republicans by a seven-to-one margin in the city, raising the possibility that the work stoppage could adversely impact Democratic presidential nominee Hillary Clinton and Senate Democratic candidate Katie McGinty.
Pennsylvania is regarded as a key presidential swing state. The Senate race between McGinty and incumbent Republican Pat Toomey is a virtual tossup, one of half a dozen close races in the country that will determine which party controls the Senate.
"As part of our get-out-the-vote effort, we are encouraging voters to make backup plans," Brandon Cwalina, a spokesman for the Pennsylvania Democratic Party, said in a phone interview.
The contract expired at midnight on Monday after union members and system officials were unable to reach an agreement over health care benefits, pensions and issues involving worker conditions, local media reported.
(Additional reporting by Brendan O'Brien in Milwaukee; Editing by Mark Potter and Lisa Shumaker)