Election officials are warning voters that certain political speech at the ballot box is not protected

FRESNO COUNTY, Calif. (KFSN) — As in-person voting increases, Fresno County officials are reminding voters of strict laws against certain political speech.

Voters are not allowed to campaign for or support specific candidates or ballot measures within 100 feet of a vote center or mailbox.

“Prohibited actions include vocal advocacy, wearing materials bearing candidates’ names, likenesses or logos. The distribution of buttons, stickers, pens or other materials containing campaign information,” said James Kus, Fresno County county clerk and registrar.

Kus says his election officials are ready to enforce the law. They will ask voters to remove or cover signs, shirts and flags bearing the candidates' names and logos.

However, there are exceptions.

“Material that is not on the current ballot is not subject to this ban,” Kus said. “Slogans do not fall under this ban.”

Officials say the law prevents voter intimidation, something Fresno County District Attorney Lisa Smittcamp says her office takes seriously and could prosecute.

“It is not your First Amendment right to threaten people,” Smittcamp said. “In addition, voter intimidation or interference in election operations are criminal offenses.”

The possibility of physical threats or intimidation comes against a backdrop of heightened political rhetoric that authorities fear could boil over.

ABC News obtained documents that the Department of Homeland Security's Intelligence Bureau provided to law enforcement. Government officials fear that the current environment could lead to election-related violence.

“We are not aware of any credible threats here in Fresno County related to the election on Tuesday, November 5,” said Fresno County Sheriff John Zanoni.

Zanoni says his deputies will respond to possible threats on Election Day at vote centers and drop boxes on county property.

Federal officials are also on standby. The U.S. Attorney's Office has named a county election official to oversee federal complaints about potential fraud and voting rights violations.

“If an incident with federal elements comes to the police or sheriff’s department, we would refer it to the U.S. Attorney’s Office,” Smittcamp said.

The District Attorney's Office has already received a referral regarding possible canvassing in Fresno. But officials say most voters are respectful and cooperative with poll workers.