RENEE MONTAGNE, HOST:
Around the country, election officials are checking and double checking their equipment to make sure the results are calculated accurately. Officials are under increased scrutiny this year, with Donald Trump and his allies claiming the system could be rigged. From member station KJZZ, Carrie Jung takes us to the largest county in Arizona to see how one state handles vote count security.
CARRIE JUNG, BYLINE: It's a dry run of sorts for Maricopa County elections officials. And the Ballot Tabulation Center in downtown Phoenix is buzzing.
HELEN PURCELL: This is the logic and accuracy test.
JUNG: Maricopa County Recorder Helen Purcell explains what we're hearing right now are mock mail-in ballots being sucked in and scanned through one of the counties nine tabulation machines. Officials from the Arizona secretary of state's office are here, too.
PURCELL: And the results that come off the machines have to match what they have pre-marked.
JUNG: State law requires all voting equipment from each county to pass accuracy tests like this before the general election. Karen Osborn is the county's director of elections. She says the process has evolved a lot since the 1970s, when she started working on elections.
KAREN OSBORNE: It's no longer just transporting ballots from point A to point B with only the security of two people. Now, it is multiple people doing multiple jobs, and then each one has to prove the other correct.
JUNG: Take in-person voting on Election Day, for example. After voters make their selections, the ballots are scanned. A machine records and tallies the votes and saves the paper ballots as a backup. At the end of the night, the ballots and the electronic tally will be transported by separate teams to ballot collection sites.
ELIZABETH BARTHOLOMEW: And usually we have to poll workers come from different parties.
JUNG: Elizabeth Bartholomew is a spokesperson for the Maricopa County Recorder's office. She explains, once all polling places have delivered their returns to the sites, everything is taken downtown and into the glass-enclosed ballot tabulation center that's open to the public.
BARTHOLOMEW: Everything is run in that room. Nothing is run at the polls, at the polling places. Nothing is run through Wi-Fi, through Internet. And so that way, these votes are the most secure they can possibly be.
JUNG: Poll sign-in books must match the number of votes cast at a precinct, and each county must also hand count 2 percent of the precincts for one final accuracy check. So what do elections officials in Arizona have to say about concerns the election might be rigged? Maricopa County Elections Director Karen Osborne says, in this state, it's not true.
OSBORNE: There are so many checks and balances on this system that it continues to prove itself on a daily basis.
JUNG: Back at the Ballot Tabulation Center, all of Maricopa County's voting equipment has passed inspection, which means they can now start officially counting early votes and mail-in ballots. For NPR News, I'm Carrie Jung in Phoenix. Transcript provided by NPR, Copyright NPR.