Election security updates: Officials brace for Election Day under cloud of threats

Harris is effectively tied with Trump among likely voters in an Ipsos national poll published Monday evening.

If the election were held today, half of likely voters said they would vote for Harris and 48% said Trump, the poll found.

When American adults were asked which candidate has a better plan, policy or approach to the following issues, Harris led on health care and political extremism, while Trump had more support for the economy, immigration and war/foreign issues, the poll found.

The poll was conducted Nov. 1-3 and has a margin of error of +/- 3.4 percentage points for likely voters and +/-3.0 percentage points for American adults.

-ABC News' Emily Chang and Oren Oppenheim

A close Trump adviser told ABC News Chief Washington Correspondent Jonathan Karl it's as if the former president "is trying to lose," Karl told "World News Tonight" anchor David Muir.

"The Trump campaign just sent me reams of data saying they are ahead in the early vote, they're doing everything they need to do to win, but I have to tell you, talking to senior advisers, people that have been advising Trump for a long time, I'm hearing newfound anxiety," Karl said. "They say he's been off-message."

Karl said the Harris campaign has been "feeling anxiety for a long time, but they feel like this is closing in the right direction for them" and that Trump's Madison Square Garden rally last month "was a turning point in this campaign."

A Georgia poll worker was arrested Monday and charged with allegedly sending a letter threatening to bomb an elections office in the state's Jones County last month, the Justice Department announced.

Nicholas Wimbish, 25, allegedly sent the threat after he had a verbal argument with a voter in the Jones County Elections Office on Oct. 16, according to prosecutors.

The following day, he allegedly mailed a letter to the Jones County elections superintendent purporting to be from the unidentified voter that stated Wimbish had "give[n] me hell" and was "conspiring votes" and "distracting voters from concentrating," according to prosecutors.

The letter allegedly stated that Wimbish and others "should look over their shoulder" and that the "young men will get beatdown if they fight me" and "will get the treason punishment by firing squad if they fight back," according to the DOJ.

The letter was allegedly signed, "PS boom toy in early vote place, cigar burning, be safe," prosecutors said.

During an interview with the FBI on Oct. 23, Wimbish allegedly blamed the letter on the voter he had interacted with, according to the complaint. During a search of Wimbish's personal computer, the letter was allegedly found in the print spooler, according to the complaint.

Wimbish faces several charges including mailing a bomb threat, conveying false information about a bomb threat, and making false statements to the FBI. He faces a maximum sentence of 25 years in prison on the cumulative charges if convicted, prosecutors said.

Court records do not list any attorney information for Wimbish.

-ABC News' Alexander Mallin

The Maryland State Board of Elections released a new statement on Monday aimed at correcting disinformation about ballot marking devices.

"Ballot marking devices do not flip or switch votes," the statement read. "Unfounded claims of machines flipping votes have resurfaced and circulated in many elections."

The board said it has not been able to substantiate any claims "of vote flipping or changing of votes by a ballot marking device," and said any such allegation must be submitted as an administrative complaint along with an "affidavit sworn under the penalties of perjury."

-ABC News' Beatrice Peterson