The Democratic National Committee, the Arizona Democratic Party and Hillary Clinton's campaign are expanding their challenge over voting rights to Arizona in the wake of its troubled presidential primary.
Clinton has made voter suppression and ballot laws in Republican-led states a centerpiece of her campaign as she rallies her base in the 2016 White House race.
Her campaign and Democrats plan to file a lawsuit aiming to force changes in how the state runs its elections.
The campaigns of Bernie Sanders as well as Congresswoman Ann Kirkpatrick's U.S. Senate campaign will join the lawsuit.
The groups say Republicans who control the state Legislature and Arizona elected officials are using "every legal loophole and every fear tactic" to disenfranchise minority and poor voters.
The action comes after the Phoenix area saw huge lines at polling places during the March primary.
Republican Secretary of State Michele Reagan's spokesman called the effort "a partisan attack from partisan organizations."