A labor dispute in Philadelphia could make it tougher for some voters to get to the polls next week, potentially affecting the presidential and down-ballot races.

Transit workers at the Southeastern Pennsylvania Transportation Authority went on strike Tuesday after failing to secure a new contract by Oct. 31. That leaves SEPTA and the Transportation Workers Union Local 234 with a week to hash out their differences and get the trains and buses running for Election Day.

No one can say for sure how a transit shutdown could affect voting, if at all. Like voters in other dense cities, most residents in Philadelphia probably live relatively close to their precincts and may not need public transit to reach them. But some may rely on the bus, and the greater concern is that some voters may have less time to go to the polls if the shutdown lengthens their commute.

If the strike did keep people from voting, it would most likely hurt Hillary Clinton and other Democrats who rely on high Democratic turnout in Philadelphia and its liberal-leaning suburbs. Pennsylvania is typically a Democratic stronghold in presidential races, but GOP nominee Donald Trump has tried to put the blue state in play this election. The real estate mogul gave a speech outside Philadelphia on Tuesday.

Clinton is leading Trump by 6.5 points in Pennsylvania, according to the latest modeling from HuffPost Pollster.

The Clinton campaign said it has been urging voters to make specific plans for getting to the polls next week, and expects to open hundreds of get-out-the-vote stations across the state. As for the strike, Clinton campaign spokesman Ian Sams said, “we are hopeful that both sides can come to an agreement in short order.”

There are three sticking points that brought SEPTA and the union to an impasse: health care, pensions, and workers’ breaks and scheduling. The union says SEPTA’s offer would force employees to pay thousands more dollars each year in order to maintain their current health care plans, and that it isn’t fair to cap workers’ pensions when management’s aren’t capped. The union also says many drivers have unreasonable schedules, leading to irregular shifts and breaks that aren’t long enough to use the bathroom.

SEPTA, for its part, says the final offer it made before the strike was a fair one. The agency said the union local’s president, Willie Brown, “walked away from a contract offer that would have provided his members pay raises, enhanced pension benefits, maintained health care coverage levels and continued job security, while also remaining fair and affordable for the taxpayers and riders who fund SEPTA.”

SEPTA riders aren’t strangers to work stoppages. In 2009, workers went on a strike that lasted six days. But there’s precedent for much longer shutdowns. In 1998, a strike lasted 40 days.

In this case, the looming election gives both sides an incentive to get a contract in place and get workers back on the job. Indeed, the contract expiring shortly before Election Day has probably given the union some leverage. Workers first voted to authorize a strike, but then voted not to extend negotiations if an agreement wasn’t reached by the deadline. After all, if the strike was delayed beyond the election, management probably wouldn’t have the same degree of urgency to settle on a contract.

If it can’t reach a contract by Election Day, SEPTA says it plans to seek an injunction in court that would force workers back onto the job. In order to succeed in that, the union believes SEPTA would have to demonstrate that the strike will have a serious impact on voting, and there doesn’t appear to be any good data to point to for that.

Asked if SEPTA was laying plans for Election Day beyond an injunction, spokeswoman Heather Redfern said, “At this point we’re hoping to settle it before that time.”