"I think it's important that he knows that he is supported even though a lot of people say, 'He is not my president,'" Beth Gadzick, who was standing in line holding a Trump flag, told CNN. "I'm sorry but he IS your president, and I think it's important to be united as one country."
Gadzick was among the hundreds who lined up to make sure they had a good view at the rally, which takes place a day after Trump's primetime speech outlining his Afghanistan strategy
. Temperatures hit triple digits in the late morning; thousands are expected to descend downtown for the evening event.
"Flake is another one like McCain, he's turned into a RINO," Gadzick said, an acronym of the expression "Republican in name only." "I'm like, he's your president, you're a Republican, you should support him."
Early in the afternoon, those who waited in line were relatively low-key; many were just trying to stay cool and chatting with one another.
Some in line speculated Trump would pardon Joe Arpaio, the controversial former Maricopa County sheriff who was convicted of contempt by a federal judge last month.
"I think he should," said 20-year-old Nick Hughes, from Litchfield Park, Arizona. Hughes was sporting a giant American flag as a cape. Hughes said he wanted to attend the rally "to show my support with all the protests going on and all this negativity."
When asked on Air Force One on the way to Arizona, White House press secretary Sarah Huckabee Sanders said no news would be made Tuesday
on a would-be Arpaio pardon.
Other rally attendees wondered whether Trump would officially endorse Flake's opponent Dr. Kelli Ward,
whom the President recently tweeted about. Dozens of people held Ward signs or sported pro-Ward stickers as they stood in line.
At the front of the line, members of the Arizona GOP set up a table to encourage voter registration. Cinthia Love, of Scottsdale, Arizona, was among the volunteers helping sign people up.
"It's time for us to unite for the betterment of this country," Love, who was sporting bedazzled American flag gear and a necklace of an American Eagle, told CNN.
Love said she hopes Trump does pardon Arpaio, who she said she believes he has "done a lot for this state." She also hopes Trump touches on health care and immigration during his speech.
Sisters Amricela Godinez, 25, and Ana Rose, 36, who are Mexican-American, came because they said they "support the President no matter what."
"I don't think he's racist," Rose said. "I think a lot of people that follow him may be, but I also think a lot of people that follow him are not."
As far as immigration goes, Rose said she thinks illegal immigration "is a problem for every country," including the US.
"You can't not have rules," she said. "Trump is our president, whether people like it or not. We support him because we support our country."
Nearby the convention center, a handful of vendors had set up shop, selling gear ranging from "I came to kick ass and covfefe" shirts to "hot chicks for Trump" buttons.
"I knew it was going to be crazy," My Campaign Wear employee Codi Herrera, of Mesa, Arizona, told CNN. "We've been following Trump since he announced his candidacy. It's our busiest time."
Some businesses and schools closed early in anticipation of the rally and counter protests.
As supporters waited for the convention doors to open at 4 p.m. local time, others in Phoenix geared up to protest.
Almost a dozen protests -- organized by a handful of various progressives and anti-bigotry groups -- were scheduled for the afternoon.
Democrats in Arizona, including Phoenix Mayor Greg Stanton, are criticizing Trump for even visiting the state -- particularly for a campaign-style rally, following the violence at the "Unite the Right" rally in Charlottesville, Virginia, last weekend. The protest led to the death of counterprotester Heather Heyer, and two police officers were killed in a helicopter crash monitoring the protests.
One organization, called Indivisible Surprise, planned a "Purple for Heather" rally.
Another organization, Puente Human Rights Movement, is holding a "White Supremacy Will Not Be Pardoned" rally.
The Trump rally kicks off at 7 p.m. local time, 10 p.m. ET.