PHOENIX (AP) — President Donald Trump's latest campaign stops Tuesday will take him to one of the nation's biggest hot spots for the coronavirus outbreak.

With cases soaring in Arizona and hospitals growing increasingly crowded with COVID-19 patients, the state has become a leading battleground in the politically charged debate about mask-wearing, which the president has fanned.

Trump is scheduled to visit Yuma to look at the border wall he's championed before flying to Phoenix to speak at a “Students for Trump” rally. Both cities and counties he'll visit have ordered people to wear masks in public — a step the president has resisted, even while touring a mask factory during his last stop in Arizona on May 5.

Phoenix Mayor Kate Gallego, a Democrat, said Monday she doesn't think the president can safely hold his planned event in her city, and called on him to wear a mask.

“Everyone attending tomorrow’s event, particularly any elected official, should set an example to residents by wearing a mask,” Gallego said in a statement. “This includes the President.”

Gallego said police won't be handing out tickets if people at the rally aren't wearing masks. The city's approach has been to educate, not ticket, violators, she said.

Trump's Arizona events come on the heels of his rally Saturday in Tulsa, Oklahoma, which was billed as the president's return to the raucous arena rallies that have helped define his political movement. But the turnout was meager, which many empty chairs visible in the arena.

Arizona has long been a stronghold for Republicans but its fast-changing demographics have made it a prime pickup opportunity for Joe Biden, the presumptive Democratic nominee. The change is driven in large part by a growing Latino population and especially the shift of suburban voters away from the GOP during the Trump era.

Trump's plans for large rallies have caused consternation among public health officials who've warned against gathering in big groups to limit spread of the coronavirus.

Arizona, in particular, is seeing disturbing trends in several benchmarks, including the percentage of tests that prove positive for the virus. The state's positive test rate is at a seven-day average of 20.4%, well above the national average of 8.4%. When the positive test rate rises, it means that an outbreak is worsening — not just that more people are getting tested.

Gov. Doug Ducey, a Republican and Trump ally, lifted his stay-home order in May but said social distancing should be maintained. He carefully avoided criticizing people who violated the recommendations and declined to order people to wear masks. But seeing worrying trends, he reversed his position last week and allowed cities and counties to impose their own mask mandates. Most, including Phoenix and Yuma — and the counties where they sit — have issued such orders.

Still, Ducey said he would not intervene to discourage Trump's rally.

“These are voluntary events and people will voluntarily make the decision," Ducey said at a news conference last week. “We’re going to protect people’s rights to assemble in an election year.”

Officials at the Dream City Church said on their website that they leased the North Phoenix megachurch to Turning Point USA, a group of conservative activists on college campuses, and found out later that Trump would be there. Hosting the rally doesn't constitute an endorsement of Trump, they wrote.

On Monday, church leaders posted a Facebook video saying they've installed an air purification system that can eradicate the virus from the air, claiming people in the church are “safe and protected.” Details were scant about the technology, but even if it's effective, it couldn't block person-to-person transmission by people in the crowd.

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Associated Press writer Bob Christie contributed to this report.