A federal judge in Los Angeles denied a Trump administration request Wednesday to immediately block California elections officials from counting the ballots of 20,000 voters whose citizenship the administration questions in a blistering opinion.

U.S. District Judge David O. Carter ruled that the administration's allegations were "not credible" and that the intervention it sought would violate a host of federal laws, sow chaos in the ongoing midterm election, likely lead to the disenfranchisement of legitimate voters and foster future political meddling in elections.

"This request violates longstanding constitutional principles mandating that states have control over their elections," Carter wrote. "If [the Trump administration's] last-minute request for relief were granted, either party could create chaos for their own political purposes to disrupt the election process."

Carter, an appointee of President Cli...