A new lawsuit challenges Pennsylvania's absentee ballot deadlines, saying the window between the last day to request a ballot and the deadline to return it is so short that voters cannot vote even though they followed the law.

That makes the law unconstitutional, the ACLU of Pennsylvania argues on behalf of nine voters in the suit, because it breaches the state constitution's guarantee that elections "shall be free and equal." The suit also argues that the law violates the Equal Protection Clause of the 14th Amendment to the U.S. Constitution.

In recent midterm elections, more than 2,000 absentee votes have been rejected for arriving after the deadline.

"The integrity of Pennsylvania elections is threatened by the disenfranchisement of so many otherwise qualified voters," the lawsuit reads.

By state law, voters have until one week before Election Day to request an absentee ballot, which is sent to them by mail.

They have until 5 p.m. that Friday — three days later — to return their filled-out ballot to be counted. If the ballot takes two days to travel from county election officials to the voter and then two days to be sent back, the ballot will miss the deadline and be rejected.

>> READ MORE: Pa.'s absentee-ballot problem: Votes come in late because of tight deadlines

"Frankly, the people we heard from — many very angry people who felt they had done everything right — they had met the deadline for applying for a ballot. Some of them went to pretty extensive lengths to get them by the deadline and didn't get to vote," said Molly Tack-Hooper, an ACLU attorney in Philadelphia. "We wanted to see if there was something we could do to prevent them from being disenfranchised."

The lawsuit, which cites an August article from the Inquirer, was filed Tuesday in Commonwealth Court by the nine voters and the ACLU. The Lawyers' Committee for Civil Rights Under Law is also representing the plaintiffs. The nine voters suing the state are from several counties, including Philadelphia, Montgomery, Allegheny, and York. All nine requested absentee ballots by the deadline, the lawsuit states, but received their ballots too late to be returned in time.

"There are countless others like them who will lose the right to vote in future elections unless the Friday absentee ballot receipt deadline is struck down," the suit reads.

The deadlines are set in the state Election Code. The suit names five defendants, all in their official capacities: Robert Torres, acting secretary of state; Jonathan Marks, commissioner of the Bureau of Commissions, Elections, and Legislation in the Department of State; Joe Scarnati (R., Jefferson), president pro tempore of the state Senate; Mike Turzai (R., Allegheny), speaker of the state House; and Gov. Wolf.

Signaling that the Wolf administration probably wouldn't fight the suit, Wanda Murren, spokesperson for the Department of State, said in an email Wednesday that the administration already had "proposed a series of reforms to make voting more convenient, including modernizing absentee voting and the deadline."

All states have election deadlines, but the data show that Pennsylvania's is among the most restrictive for absentee ballots. It is one of few states in which the majority of rejected absentee ballots are due to missed deadlines.

In the 2014 general election, for example, 2,030 of 2,374 rejected absentee ballots were disqualified for missing the deadline.

Only three jurisdictions had higher rejection rates due to missing the deadline: South Carolina, with all 533 rejected ballots coming from missed deadlines;  American Samoa, 3 out of 3; and Delaware, 60 of 62.

New Jersey has the same deadline for requesting an absentee ballot — but voters can return them through Election Day, giving them four more days. In 2014, one in five rejected absentee ballots in New Jersey were for missing the deadline.

The problem has become more severe in recent years, state and county election officials say, because the U.S. Postal Service in 2012 closed numerous distribution centers across the state, increasing the time it takes for mail to arrive.

Election officials say there is little they can do, because the deadlines are written into state law. They urge voters to request and return absentee ballots early. But after 5 p.m. on the Friday before Election Day, there's nothing they can do.

And to change the law in this case, Tack-Hooper said, the ACLU would rather ask the courts to take action than hope lawmakers do.

"Obviously, the General Assembly could step in and fix this on their own," she said, "but they have a lot to do, and we weren't going to sit around and wait for that."

>> READ MORE: Pa.'s absentee-ballot problem: Votes come in late because of tight deadlines