Days before the midterm election, the Department of Justice is demanding Washington elections officials set aside the ballots of more than 400 people, asserting they are noncitizens who are illegally registered to vote.

At a news conference Monday, Charles Neil Floyd, the acting U.S. Attorney for Western Washington, said he’d notified Secretary of State Steve Hobbs of the potentially illegal voters in a letter, and urged him to take immediate action.

Floyd said a federal investigation found “with high confidence” that noncitizens “are voting in the state of Washington in state and federal elections, and many of them have voted multiple times.”

The list of potentially illegal voters cited by Floyd represents a tiny fraction of Washington’s 5 million-plus registered voters. But he said the federal review so far was only based on a small sample.

“This is not the full number of noncitizens who have been voting in Washington.…