On Friday, Walz and Harris staged a rally at a packed Desert Diamond Arena in Glendale, Ariz., where they were introduced by U.S. Sen. Mark Kelly, D-Ariz., and his wife, former U.S. Rep. Gabrielle Giffords, D-Ariz.

Kelly, who was on Harris’ shortlist as a possible running mate, proclaimed his support for the Harris-Walz ticket, while Giffords, the survivor of an assassination attempt in 2011, related her story of learning to speak and walk again after the gun violence incident.

“We are living in challenging times,” she told the crowd. “We’re up to the challenge.”

In a theme that was expected to be repeated Saturday in Las Vegas, Harris in Arizona concentrated her attention on the issue of immigration, responding to frequent charges from the GOP ticker of former President Donald Trump and Sen. JD Vance of Ohio that she “oversaw” the Biden administration’s “failed immigration policies” as its “border czar.”

Much as Kelly did earlier this year in the Senate, Harris voiced strong support for a bipartisan border security bill brokered by Sen. Kyrsten Sinema, I-Ariz., and backed by President Joe Biden, under which thousands of additional Border Patrol agents and Customs and Border Protection personnel would have been added.

The agreement, however, failed in the Senate in May after Trump urged Republicans not to give Biden a pre-election legislative victory.

“Earlier this year, we had a chance to pass the toughest bipartisan border security bill in decades,” Harris said. “But Donald Trump tanked the deal because he thought by doing that it would help win an election. But when I am president, I will sign the bill.”

Local and national Republicans kept up their attacks on the Democrats over immigration in Las Vegas on Friday prior to the rally there.

At the state’s GOP headquarters in Henderson, Nev., state party chairman Michael McDonald again referred to Harris as the Biden administration’s “border czar,” asking reporters, “How’d that work out?”

Democrats dispute the characterization that Harris has ever been placed in charge of securing the nation’s southern border as a “czar.” Rather, they say, in 2021 she was chosen to head a wide-ranging, cross-agency effort to address the root causes of illegal border crossings through diplomatic engagements with Latin American nations such as Guatemala, Honduras and El Salvador.

Harris this week has sought to toughen her message on immigration with the unveiling of a new ad running in Arizona and Nevada, emphasizing her support of the bipartisan border bill and touting her credentials as a “border state prosecutor.”

“Fixing the border is tough, so is Kamala Harris,” the ad states.