Gov. Gavin Newsom of California on Friday vetoed a bill that would have helped some undocumented immigrants buy homes in the state, moving quickly to extinguish a potential flashpoint in the presidential election.

The proposal, which would have expanded an existing loan program for first-time home buyers to include undocumented immigrants with Social Security or taxpayer identification numbers, had been widely criticized by Republicans as Democratic largess provided to immigrants living in the United States without authorization.

The bill moved through the California Legislature late last month as former President Donald J. Trump and Republicans continued to attack Democrats as lax on immigration. Mr. Trump, in his bid to return to the White House, has already tried to blame Vice President Kamala Harris for various liberal policies in her home state of California, including those in which she played no role.

California Republicans argued that the state should prioritize legal residents for any state home-buying assistance, but the bill passed easily along party lines in the Legislature, where Democrats have a supermajority in both houses. By that time, it was already a cause celebre on right-wing media outlets.

On his social platform X, Elon Musk posted last week that “half of Earth should move to California, given all the incentives to do so.” And Mr. Trump this week capitalized on the conversation, vowing in a speech to the Economic Club of New York in Manhattan to bar undocumented immigrants from obtaining mortgages.

Home loans to undocumented people living in the United States are legal but rare. However, California Democrats have pointedly sought to remove immigration status as a condition of receiving a number of state benefits, including health insurance, college financial aid and, most recently, campus jobs at state-funded universities.