Nov 2 - Acting on the eve of the US midterm elections, the Supreme Court quickly rejected on Monday a bid by President Donald Trump's administration to temporarily block California from counting mail-in ballots from more than 20,000 registered voters who federal officials allege are likely non-US citizens. The justices denied the Justice Department's emergency request just hours after it filed it, shutting down the administration's claims over disputed ballots that could have affected thousands of voters and injected uncertainty into election outcomes.

The decision represented another defeat for Trump as his fellow Republicans fight to retain control of Congress in Tuesday's midterms. California is the most populous US state and a Democratic stronghold. The administration intensified its focus on alleged noncitizen voting in the run-up to the midterms. Multiple studies and state audits show that ineligible voting, including by noncitizens, is rare. The Supreme Court's brief, one-sentence order on Monday did not offer any explanation of its action, as is common when it handles emergency matters.

No justice publicly dissented from the decision. The court also did not ask California for a response to the administration's request, a step that, when taken, usually signals serious consideration of an emergency case.A federal appeals court refused the administration's request on Friday. "Once California commingles the challenged ballots with lawful ones, there is no way to get the challenged ballots back," the Justice Department said in its request to the Supreme Court. The administration had demanded that California separate any allegedly unlawful ballots from other ballots and not count them until those voters are determined to be US citizens.

"This latest move reeks of desperation, and is another attempt to undermine our elections and trample on the rule of law," California Attorney General Rob Bonta, a Democrat, said in a statement after the administration's filing earlier in the day, vowing to "defend the fundamental right to vote and push back against this lawlessness." Trump has made false claims about widespread US voting fraud including in the 2020 election lost to Democrat Joe Biden.

"We will continue pursuing every available legal avenue to protect the integrity of our elections and ensure federal law is enforced," acting US Deputy Attorney General Trent McCotter said in a social media post after the administration's filing earlier in the day.CONSTITUTIONAL QUESTIONSThe US Constitution assigns the responsibility of administering elections to states, though the federal government has some oversight. The lawsuit marked a rare federal intervention in the voting process and signaled a willingness by the administration to contest the election results in court.

The administration already sought to restrict voting by mail — a mode of casting ballots used more often by Democratic-leaning voters — but the Supreme Court in September rebuffed that effort. And a federal judge on Sunday dismissed the administration's lawsuit concerning the US Senate race in Alaska.

The list of 20,000 registered voters was amassed by the US Department of Homeland Security and sent to California officials and to Los Angeles County officials. The Justice Department sued in federal court on October 15, claiming California is unlawfully preventing its enforcement of a 1996 US law that makes it a criminal offense for noncitizens to vote in federal elections. The department said California's action violated the Constitution's Supremacy Clause, which holds that federal law generally preempts state law.

California has said that the state's safeguards against noncitizen voting are robust and that the lawsuit threatens to deprive 20,000 people of their right to vote based on vague accusations. The administration's process for scrutinizing voter lists to identify noncitizens is flawed and likely rife with errors, it said in court papers.

California has 52 seats in the House of Representatives, more than any other state. Democrats need a net gain of four House seats to win a majority in the chamber.'BEND TO THE WILL'US District Judge David Carter in Los Angeles denied the administration's request on October 28. "Never before in American history has the federal government, on the eve of an election, sought to coerce a state and local government to abandon their own constitutional elections procedures and bend to the will of the executive branch," Carter wrote.

Carter raised concerns over the reliability of the administration's data, noting that people recently flagged by the federal government as noncitizens on voter rolls in other states have repeatedly turned out to be naturalized US citizens. "If the executive can discount votes and threaten an ongoing election due to unproven allegations, then our democracy is in danger," Carter wrote.

The San Francisco-based 9th US Circuit Court of Appeals also refused on Friday to block the ballots, emphasizing the state's power over election procedures and California's "comprehensive statutory scheme to ensure the integrity of its elections," including a system for canceling registrations if a voter is shown to be ineligible.

The administration has taken an increasingly aggressive approach toward how states run elections. The Justice Department has told election officials in all 50 states that they could face criminal prosecution if they knowingly allow noncitizens to remain on their rolls or cast ballots.

But it also has lost a series of lawsuits seeking to obtain voter rolls, including sensitive personal information, from dozens of states. (Reporting by Andrew Chung; Editing by Will Dunham)