PHOENIX (AP) Inside a squat building ringed with a chainlink fence and concrete barriers in downtown Phoenix, election workers on Nov. 5 will begin a grindingly slow tally of every ballot cast in the vast expanse of stucco and saguaro that is Maricopa County, Arizona.

In what has become the nations ultimate swing county, the count here could determine whether Democrat Kamala Harris or Republican Donald Trump will be the next U.S. president. It also is likely to determine the winner of a closely watched race that could decide which party controls the U.S. Senate .

It is one of the most consequential battlegrounds in the country. That means voters, campaigns and people around the world sometimes must wait more than a week to learn who won the county, and with it, statewide races in the swing state of Arizona. This year, election officials warn it could take as long as 13 days to tabulate all of the ballots in Maricopa.

The drawn-out count has made the county a center of election conspiracy theories spawned by Trump. Its also made Maricopa a key part of the former presidents campaign to install those who supported overturning the last election in 2020 into positions overseeing future ones.

But the reason it takes so long is simple. With its 4.5 million residents, Maricopa has a higher population than nearly half of the states in the country and is home to 60% of Arizonas voters. Election workers must follow voting laws which were approved by Republican-controlled legislatures that slow the count. And it is one of the few counties in the U.S. that is so evenly divided politically that races are often close.

Thats made the county the center of everything, says Joe Garcia, a leader of the Latino activist group Chicanos Por La Causa, noting it is the population center of Arizona, its center of growth and home to the state capital.

So the power structure, the money and the growth is all here in Maricopa County, he said. If you can win Maricopa County, youre probably going to win the whole state of Arizona.

Maricopas position isnt just at the center of Arizona politics. The county has been a regular stop for presidential candidates as they look to clinch Arizonas 11 electoral votes including Trump and Harris and their campaigns this year and it is a fulcrum on which nail-biter races that can determine control of the House of Representatives and U.S. Senate pivot.

The fast-growing county also has become home to a stew of key demographic groups in the battle for the White House: a growing Latino population, retirees, younger, newly arrived voters and a broad and deep conservative population wrestling with a pivotal splinter group college-educated, more affluent Republicans whove soured on the partys more pugnacious, and at times anti-democratic, turn under Trump.

It wasnt always like that.

A small town booms

Judy Schwiebert grew up in western Phoenix in the 1960s, when the now-booming city was what she describes as a pretty small town and the biggest event of the year was the three-day rodeo.

Everything stopped for the rodeo parade, as horse-drawn carriages, marching bands and dancers made their way through town. Schools closed for the full three days, recalls Schwiebert, who is now a Democratic state representative. In 1969, the county was still home to fewer than 1 million people, less than one-quarter the size it is today. With about 4.5 million residents, Maricopa County now has a population similar to the entire state of Kentucky.

Over the years here Ive seen it grow and grow, Schweibert said.

The area became a magnet for conservatives like John Kavanagh, a retired New York Port Authority Police officer. After 20 years of policing, Kavanagh and his wife headed west, to Maricopa County. They went in 1993, because his wife couldnt stand the cold in New York and Florida had too much humidity and was overstocked with New Yorkers.

Kavanagh was like a lot of other people who moved to Arizona in the 1990s middle-class folks fleeing colder places and what they saw as economic and political dysfunction for a sunny, affordable, and what they perceived as a cleaner city.