The Trump administration on Thursday sued the state of California and a Los Angeles County official, seeking to temporarily block the state from counting mail ballots submitted by voters it suspects are noncitizens.
The suit, which would apply to some 20,000 people in the state the administration has cast as “likely noncitizens,” is a long shot. But it opens a new front in the administration’s legal battles with local election officials weeks before the midterm elections.
Over the past 18 months, the Trump administration has sued California and other states over voter rolls, and has lost resoundingly in court. This time, the Justice Department is trying a new strategy, seeking a court order to prevent the counting of votes from the 20,000 people in the state identified by the Department of Homeland Security “until their citizenship status can be determined.”
Attorney General Todd Blanche said in a statement that California had received ample warning. It was given “an opportunity to self-correct its records, and we requested that it segregate the suspected illegal ballots for the upcoming election,” he said. “California has refused to comply and intends to facilitate noncitizens in voting, which is a violation of federal law.”
Similar past claims of thousands of illegal voters have fallen apart under scrutiny. Last month, election officials in Nevada said that they had examined a list provided by homeland security officials of 185 names of supposed noncitizens who had been improperly registered to vote, and found that every person on the list was a lawful citizen.
“I think this lawsuit is going to have some very serious problems, and raises questions about what the reason is for D.O.J.’s timing,” said David Becker of the Center for Election Innovation and Research, a nonpartisan group that advises election officials. He noted that the administration’s past claims of noncitizen voting in other states had been found to be “vastly inflated” and “rife with errors.”
Mr. Becker said that about six million ballots had already been cast via early voting in different states, and that the process had gone smoothly.
In recent months, President Trump has claimed that hundreds of thousands of people have voted illegally. Reviews by election officials and criminal investigators have found small numbers of people who have been caught voting illegally every election cycle — but not in quantities that would come close to deciding the winners of major races.
California officials vowed to fight the administration’s effort.
“This is a sad, desperate attempt by Trump to use his politicized Justice Department to try to suppress California voters just three weeks before Election Day,” Gov. Gavin Newsom of California, a Democrat, said on social media. “Courts have made clear the federal government has no role in running state elections.”
Rob Bonta, the attorney general of California, said that the state would not comply with the administration’s demands and instead would respond in court.
“This is nothing more than their ongoing, dangerous, reckless, scorched-earth, widespread attempt to advance conspiracy theories about widespread voter fraud that doesn’t exist,” he said.
U.S. elections are administered and supervised by state and local authorities, and the federal government plays a limited role. The Trump administration, however, has pushed to assume far greater authority over the management of state voter rolls, with little success.
Earlier this year, Justice Department officials warned in letters to state and local election officials that they could be prosecuted if they did not take sufficient steps to remove noncitizen voters from the rolls.
The administration has escalated its fight with California over the last week.
Days earlier, federal authorities sent a thumb drive of roughly 20,000 names they suspected were noncitizens registered to vote in California to election officials in Los Angeles County, demanding they act within 48 hours.
In a blistering letter, Shirley N. Weber, California’s secretary of state, said the data sent by the administration “lacks both the detail and function to be of any investigative use.” She added that “nowhere has the federal government clarified the basis for suspecting — not even confirming with any level of certainty — the listed individuals are noncitizens.”
The administration’s demands and deadline, she said, “threaten thousands of Californians’ right to vote, based on unverifiable information or methodology that you still fail to explain or provide.”
The election officials in Los Angeles County said they had not opened the thumb drive “because doing so would conflict with established data privacy and information security protocols.”
Dean Logan, the registrar in Los Angeles, said in a statement that “we do not consider the device a secure medium.”
To compile the administration’s list of “likely noncitizens” on the voter rolls, Department of Homeland Security officials use “third-party software to develop high-, medium- or low- confidence matches between voter information and information about that individual compiled by the software program,” the lawsuit said.
Employees at the U.S. Citizenship and Immigration Services agency then compare those on the “high confidence” list with an “alien number” in their own database. They search their internal records for any evidence of citizenship, while also reviewing State Department records and Social Security Administration data, the lawsuit said.
That list is then forwarded to Homeland Security Investigations, an arm of Immigration and Customs Enforcement, “to perform additional, manual review of the relevant matches.”



















