Kamala Harris and Tim Walz rallied a packed arena outside Phoenix, Arizona, on Friday – drawing perhaps the largest Democratic crowd of the election cycle this year.

The presumptive Democratic presidential nominee, her running mate and the local leaders who joined them on stage whipped up the crowd, discussing immigration, abortion rights and Indigenous sovereignty.

Noting the Indigenous leaders in the room, Harris also said: “I will always honor tribal sovereignty and respect tribal self-determination.” Indigenous voters are credited with helping deliver Arizona to Joe Biden in 2020; the state is home to 22 federally recognized tribes.

At one point during her speech, Harris was interrupted by protesters chanting “free, free Palestine” and other messages in support of Gaza. She stopped her speech to address the protesters.

“We’re here to fight for our democracy, which includes respecting the voices that I think we are hearing from. Let me just speak to that for a moment and then I’ll get back to the business at hand,” she said. “I have been clear: now is the time to get a ceasefire deal and get the hostage deal done. Now is the time. And the president and I are working around the clock every day to get that ceasefire deal done and bring the hostages home.” Her statement represented a noticeable change in tone from her approach to Gaza protesters in Detroit on Thursday.

Harris and Walz took the stage at the Desert Diamond Arena, a venue that can hold 20,000 people. Although official estimates are not yet available, the Harris campaign confirmed that more than 15,000 people attended the Phoenix rally. On stage, in front of attendees waving signs that read “Coach!”, Walz said the rally “might be the largest political gathering in the history of Arizona”.

“It’s not as if anybody cares about crowd sizes or anything,” he added.

Other Harris campaign events this week that have drawn crowds of up to 15,000, invoking the ire of Donald Trump, who claims to have “spoken to the biggest crowds”.

The Harris-Walz rally represents a renewed push to put the Sun belt back on the map for Harris’s still young campaign. Before Friday night, the state appeared to be leaning red, with Trump leading Harris by single digits in recent polls. But by the evening of the rally, Harris and Trump appeared neck and neck in the state, with polling from FiveThirtyEight showing Harris’ 44.4% closely following Trump’s 44.8%.

Polls on Friday morning showed Harris narrowly leading Trump nationwide.

Despite the large crowd, Harris reminded attendees: “We are the underdog.” She added that hard work would be required to win the election, in a short period of time. Harris officially became the presumptive Democratic nominee on Monday and announced her running mate on Tuesday, after Biden withdrew from the election on 21 July.

“I also bring greetings from our incredible president, Joe Biden,” Harris said. Earlier in the day the White House had announced Biden and Harris would attend their first joint event since the president pulled out of the race.

Speaking in a border state where immigration often ranks as a top issue among voters, Harris struck a tough, but progressive, tone – emphasizing her history as a prosecutor who “went after the trans-national gangs, the drug cartels and the human traffickers” but also calling for a pathway to citizenship.

“We know our immigration system is broken and we know what it takes to fix it: comprehensive reform. That includes strong border security and an earned pathway to citizenship,” Harris said.

While border apprehensions have dropped nationwide, they’ve remained high in Arizona – where voters will decide in November whether to make unlawfully crossing the border a state crime.

Her statements echoed a campaign ad published yesterday, saying Harris would “hire thousands more border agents and crack down on fentanyl and human trafficking”. Republicans have criticized Harris’ handling of immigration, saying she was Biden’s “border czar”, and an ad released by a pro-Trump super Pac last month blamed her for a “chaotic mess” at the border. Harris was tapped by the Biden administration to address the root causes of migration.

Abortion rights have been another key issue in Arizona since the supreme court overturned Roe v Wade in 2022. Harris noted that many states, including Arizona, had laws with “no exceptions for rape or incest”.

Abortion is currently restricted after 15 weeks of pregnancy in Arizona, although a high profile state supreme court ruling had temporarily reinstated a near-total ban earlier this year. Voters will evaluate a ballot measure this November that would codify the right to an abortion until fetal viability.

Long a Republican bastion, Arizona swung blue in 2020 when Biden defeated Trump by fewer than 11,000 votes, thanks to a coalition of Native Americans, Latinos, young people, white suburban voters and moderates who had traditionally voted Republican but were disenchanted by Trump.

Democratic strategists had wondered if the Arizona senator Mark Kelly, who has won two difficult elections, might have helped Harris cement that coalition as her vice-president. This was Harris’ first visit to the state since she announced Walz as her running mate.

Kelly and his wife, the former US representative Gabby Giffords, spoke before Harris and Walz. Giffords and Walz were freshman members of Congress together in 2007, before Giffords was shot in an attempted assassination in 2011. Giffords joined Walz in Minnesota in 2023 when he signed a package of gun safety measures into law.

Representative Ruben Gallego also spoke at the beginning of the rally. Gallego is challenging Trump’s disciple Kari Lake for Arizona’s open US Senate seat this November.