Vice President Kamala Harris said on Saturday that she would seek to end federal income taxes on tips if she were elected president, mirroring a policy proposal that former President Donald J. Trump made earlier this year.

The proposal from Ms. Harris — which she announced in Las Vegas, where thousands of casino employees depend on tipped wages — is a priority of Nevada’s influential Culinary Workers Union. Both Ms. Harris and her running mate, Gov. Tim Walz of Minnesota, recognized the union in their remarks to a packed basketball arena on Saturday night.

“When I am president,” Ms. Harris told the Las Vegas crowd, “we will continue our fight for working families of America, including to raise the minimum wage and eliminate taxes on tips for service and hospitality workers.”

The “no tax on tips” pitch has garnered bipartisan support since Mr. Trump first floated it in June, including from Senator Ted Cruz, the Texas Republican, and both of Nevada’s Democratic senators, Catherine Cortez Masto and Jacky Rosen. Mr. Trump also announced his support for the policy in Las Vegas.

The former president responded immediately to Ms. Harris’s proposal on Saturday night, posting on his social media website, Truth Social, that she had “copied” his own. “This was a TRUMP idea,” he wrote. “She has no ideas, she can only steal them from me.”

The Las Vegas stop was the last public event of a five-city introduction of the Harris-Walz ticket. As with the other rallies, Ms. Harris and Mr. Walz drew a crowd many times larger than any that had shown up for President Biden while he was seeking re-election.