Voters in Arizona had to wait in line for hours to cast ballots. Here’s why that matters.

On Tuesday evening, as polls closed in Arizona, reports began emerging that voters in the state’s most populous county, Maricopa County, were waiting in hours-long lines to cast ballots.

Aracely Calderon, a 56-year-old woman living in Phoenix, became the last person to cast a vote, at 12:12 am local time, after waiting five hours in line. Calderon, who was born in Guatemala, became a naturalized citizen in 2012.

“I’m here to exercise my right to vote,” she told the Arizona Republic, explaining why she had waited in a line that spanned more than 700 people and four city blocks. Many other would-be voters, discouraged by the lines or unable to wait because of work schedules, never cast ballots.

The excessive wait times resulted from a decision by Maricopa County officials to cut the number of polling places available across the county by 70 percent — from 200 in 2012 to just 60 in Tuesday’s election. That meant that across the county, each polling place served more than 21,000 eligible voters.

One polling place for 21,000 eligible voters is already stretching resources pretty thin. According to a report from the 2014 election administration and voter survey, each polling location in the US served an average of 1,700 eligible voters.

But the distribution of polling places was also uneven, with more precincts placed in white neighborhoods than ones where more minority voters live. In Phoenix, where the majority of residents are Hispanic, black, or another minority, each polling place served 108,000 residents. In Peoria, a city with a majority white population, each polling location was allocated to 54,000 residents.

Before 2013, Maricopa would have had to seek permission from the US Justice Department to alter its number of polling places. That’s because Arizona was one of 16 states where jurisdictions with a long history of voter discrimination had to submit any voting procedure changes under Section 5 of the Voting Rights Act.

Since 1975, the Justice Department has barred 22 voting changes from taking effect in Arizona because they would have negatively impacted the state’s Native American and Hispanic voters. Also in 2013, the Supreme Court overturned Arizona’s notorious voter ID law, which would have made it harder for foreign-born citizens to register to vote.

But in 2013, the Supreme Court ruled in Shelby County v. Holder that the Voting Rights Act unfairly discriminated against states required to check voting changes with the federal government, essentially cutting the teeth out of the civil rights-era law.

Since that decision, jurisdictions like Maricopa County have been free to make any voting changes they saw fit, without regard to how they might affect minority voters. Hence how the situation got so bad in Phoenix on Tuesday.

The Justice Department still does have jurisdiction to open investigations into individual cases of fraud, and on Wednesday, Phoenix Mayor Greg Stanton wrote the department a letter asking for them to look into the situation.

“Throughout the county, but especially in Phoenix, thousands of citizens waited in line for three, four, and even five hours to vote,” Stanton said. “Many more could simply not afford to wait that long, and went home.”

The long lines are particularly notable because they represent one of the first major mishaps in the first presidential election year in more than 50 years without Voting Rights Act protections. It’s fair to expect, then, that Arizona is not a one-time example of incompetence, but rather the first in a string of incidents to come.