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A worldwide Microsoft-based computer outage early Friday crippled the electronic systems Arizona's two largest counties use for early voting, forcing election officials to scramble to switch to backup plans to continue early voting for the state's primary election.

The outage affected equipment that Maricopa and Pima counties use to check in voters at polling places, verify voter eligibility and print ballots. It did not affect machines the counties use to count ballots, which are not used during early voting because voters place their completed ballots in envelopes to be counted later.

The power outage occurred in the middle of the night, and once polling places were open, each county responded differently. Maricopa County opened only four of its 41 scheduled locations at 9 a.m., where new equipment was readily available. Pima County decided to open all six of its scheduled locations at 8 a.m., but switched to provisional voting. It's unclear whether other Arizona counties that lost power affected early voting, but many said it didn't.

The outage came as the state was more than halfway through the early voting period for the July 30 primary election, but on a day of low early voting numbers. Only 200 people were expected to show up to vote in person in all of Maricopa County on Friday, for example.

The incident highlights certain vulnerabilities in local election systems across the country. Most of them run on Microsoft WindowsThat raises urgent new questions about how to prevent such meltdowns from happening during elections across the country, particularly the presidential election in November, and how officials will respond in the heat of voting on Election Day.

This is especially true for counties like Maricopa and Pima that rely entirely on electronic systems to register voters, verify voting eligibility and print ballots, and don't store hand-printed voter rolls or pre-printed ballots. Both counties have adopted a “vote center” model that allows voters to cast their ballots from anywhere, which requires the use of this technology.

Maricopa will replace the equipment to fix the problem.

The global outage was caused by a flawed update released by software security company CrowdStrike that affected Microsoft's Windows operating system. Some of the world's most important systemsIt's impacting hospitals, airlines, 911 call centers, and financial institutions.

The U.S. Cybersecurity and Infrastructure Security Agency, which provides election security assistance to local election offices across the country, We recommend using Crowdstrike As a tool to detect phishing attacks.

Maricopa County spokesperson Fields Moseley said the update only affected devices that were turned on during the update, not devices that were turned off.

Moseley said IT staff from all county departments began working since midnight to repair all of the county's affected computers, including equipment at polling places.

The county opted to fix issues with an unused on-demand ballot printing system and replace the equipment at polling places with updated equipment.

By 1 p.m., county teams had opened 21 polling stations, and by 3 p.m., almost all were open. Fewer than 500 voters were expected to show up at the 40 polling stations scheduled to be open on Saturday.

Pima County issues provisional ballots

Pima County's power outage affected the systems it uses to register voters and verify their eligibility to vote, according to Recorder Gabriela Cazares Kelly. As a workaround, the county had poll workers call headquarters to verify voter information, then issue voters provisional ballots.

The problem was resolved by 10:45 a.m. The county was able to remotely connect to the polling station's equipment and fix the issue, Cazares Kelly said.

During the power outage, poll workers allowed voters to fill out provisional ballots so county officials could double-check voters' voting eligibility before the ballots were counted.

“We have been planning for events like this,” Cazares Kelly said. “Our well-organized team has launched a coordinated effort to ensure that constituents can access our services with little to no disruption.”

The Arizona Secretary of State's Office announced Friday morning that it is reaching out to counties to offer IT support.

In a statement, the office stressed that the power outage did not affect vote counting in the state.

Jen Fifield is a reporter for Votebeat based in Arizona. You can contact Jen at inquiry.