Vice President Kamala Harris is set to rally in Las Vegas on Sunday night as both she and Republican Donald Trump continue to make frequent trips to Nevada, looking to gain momentum in the swing state as Election Day nears.

The rally is part of Harris' latest West Coast swing, which included making her first trip to the U.S.-Mexico border since taking over for President Joe Biden atop the Democratic presidential ticket. On Friday, the vice president walked alongside a towering, rust-colored border wall fitted with barbed wire in Douglas, Arizona, and met with federal authorities.

She attended a San Francisco fundraiser Saturday and had plans for a Sunday event in Los Angeles before heading to Nevada, with a return to Washington set for Monday night.

“This race is as close as it could possibly be," she said Saturday to a raucous crowd of donors. “This is a margin-of-error race."

Harris said even if there is enthusiasm, she's running like an underdog. And she invited people to “join our team in battleground states” to help get voters to the polls — even if it's Californians making calls from home.

On Sunday, former Arizona Sen. Jeff Flake became the latest prominent Republican to endorse Harris and Walz. He credited them with a “fine character and love of country” and said he wants a president who does not treat political adversaries as enemies or try to subvert the will of voters.

Flake, a longtime critic of the former president, joins a list of anti-Trump Republicans who have said they will vote for the Democratic ticket, not just refrain from voting for Trump. Among them is Dick Cheney, the deeply conservative former vice president, and his daughter, Liz.

On Sunday, Maryland Senate candidate Larry Hogan, a former Republican governor and a sharp critic of Trump, said Harris has yet to earn his vote, though Trump won't get it.

In Nevada, all voters automatically receive ballots by mail unless they opt out — a pandemic-era change that was set in state law. That means most ballots could start going out in a matter of weeks, well before Election Day on Nov. 5.

Harris plans to be back in Las Vegas on Oct. 10 for a town hall with Hispanic voters. Both she and Republican rival Donald Trump have campaigned frequently in the city, highlighting the critical role that Nevada, and its mere six votes in the Electoral College, could play in deciding an election expected to be exceedingly close.

Trump held his own Las Vegas rally on Sept. 13 at the Expo World Market Center, where Harris is speaking Sunday. Her campaign has frequently scheduled events in the same venue where her opponent previously spoke, including in Milwaukee, Atlanta and suburban Phoenix. During his Las Vegas event, the former president singled out people crossing into the U.S. illegally, saying Harris "would be the president of invasion.”

During a campaign stop in the city in June, Trump promised to eliminate taxes on tips received by waiters, hotel workers and thousands of other service industry employees. Harris used her own Las Vegas rally in August to make the same promise.

Fully doing away with federal taxes on tips would probably require an act from Congress. Still, Nevada's Culinary Union, which represents 60,000 hospitality workers in Las Vegas and Reno, has endorsed Harris.

Ted Pappageorge, the culinary union's secretary-treasurer, said the difference between the dueling no-taxes-on-tips proposals is that Harris has also pledged to tackle what his union calls “sub-minimum wage," where employers pay service industry workers small salaries and meet minimum wage thresholds by expecting employees to supplement those with tips.

Harris has no public schedule for Tuesday, when her running mate, Minnesota Gov. Tim Walz, squares off against Republican Ohio Sen. JD Vance for the first and only vice presidential debate of the campaign. But Harris and Walz will campaign jointly on Wednesday, making a bus tour with various stops through central Pennsylvania.

The campaign says that during that swing, both will emphasize plans to energize U.S. manufacturing, including by using tax credits to encourage steel production and overhaul federal permitting systems to increase American construction.