Officials in Georgia called for investigations into hours-long wait times to vote in the state's primary on Tuesday.
Voters reported long lines and problems with voting equipment, as Democrats went to the polls to pick a nominee in a competitive U.S. Senate race.
Jon Ossoff led a large field of Democratic contenders vying for a chance to unseat Republican Senator David Perdue, who has no primary challengers.
Ossoff, who tried and failed to flip a House seat in a 2017 special election in the most expensive House race in history, said on Tuesday in a tweet: "In light of the outrageous, unconstitutional, and unforgivable conditions at polling places this morning I reiterate that voting hours must be extended tonight. Mass disenfranchisement CANNOT be tolerated!"
Atlanta Mayor Keisha Lance Bottoms reported problems with voting machines not working and long lines that started forming as soon as the polls opened at 7 a.m.
State and local officials traded blame as poll workers grappled with new voting systems and coronavirus precautions that made lines longer.
Georgia's Republican Secretary of State, whose office opened an investigation into the voting issues, said in a statement: "Obviously, the first time a new voting system is used there is going to be a learning curve, and voting in a pandemic only increased these difficulties."
But the voter rights group that Democrat Stacey Abrams founded after narrowly losing a run for governor in 2018, said responsibility fell on the secretary of state, who they said "failed to provide Georgia's counties with the training needed to conduct today's election."