Voters endured long waits to use one of Maricopa County's 60 polling stations last month. There were at least 200 polling stations in 2012, but Republican officials said they decreased the number to save money.
Even after waiting in line for hours, some people were not allowed to vote. At least 20 Democratic voters contacted the Arizona Democratic Party to say that when they arrived at the polls, they were told that they were registered as Independents and therefore unable to vote in the closed primary.
DNC Chairwoman Debbie Wasserman Schultz said Thursday that the lawsuit is "to reverse Arizona's culture of voter disenfranchisement prior to the 2016 election."
"As Democrats, we believe the right to vote is our most fundamental right -- the right that defends all of our other rights. Democrats also know that when we see injustice, we must act," Wasserman Schultz said in a statement.
She added that the Democratic Senatorial Campaign Committee, Ann Kirkpatrick's Senate campaign and the Arizona Democratic Party are parties in the lawsuit. Clinton spokesman Brian Fallon told CNN that the campaign also is joining the DNC in the lawsuit, and the Sanders campaign Thursday afternoon added its support.
Arizona Secretary of State Michele Reagan, the Maricopa County Board of Supervisors and Maricopa County Recorder Helen Purcell are among the defendants.
A spokeswoman for the state's attorney general did not immediately respond to a request for comment. But a spokeswoman for Purcell, a Republican, told CNN last week that there were no intentional efforts to keep people from voting.
"Helen's career has been focused on trying to make voting easier and more accessible. There was absolutely no way she tried to make it harder for voters to vote or to suppress anyone from voting," Elizabeth Bartholomew said. "At the end of the day, it was just a huge miscalculation and a mistake. And we're moving forward and making changes to make sure that that never happens again."
Democratic lawmakers have claimed there were some working-class and primarily Latino neighborhoods that had no polling places.
"The Republican election officials who decided to reduce polling locations by 70% in order to cut costs later admitted they never considered the impact these actions would have on black, Hispanic or Native American communities. We know that actions like this -- disregarding and disenfranchising thousands of voters -- were easier because the Supreme Court gutted a key provision of the Voting Rights Act," Schultz wrote.
Historically, the Department of Justice had to approve any changes in voting procedure in Arizona because of the state's history of discrimination against minorities in voting. But a Supreme Court decision in 2013 allowed Arizona to begin making changes without federal oversight. Democratic officials have said if federal scrutiny had been required before making changes, the situation never would have happened.
The Department of Justice requested additional information earlier this month from Purcell regarding the matter.
Vermont Sen. Bernie Sanders, who lost Arizona to Clinton, called the situation "a disgrace" soon after the primary.
"In the United States of America, democracy is the foundation of our way of life," the Democratic presidential hopeful said. "And what happened in Arizona is a disgrace. I hope that every state in this country learns from that and learns how to put together a proper election where people can come in and vote in a timely manner and go back to work."