Trump supporters threatened election officials and their families after they refused to quash his 2020 defeat, a congressional panel has heard, BBC reported.
The speaker of Arizona's statehouse, Rusty Bowers, told the committee probing last year's Capitol riot that the harassment continues to this day.
A Georgia voter counter said she was afraid to leave home after ex-President Donald Trump specifically targeted her.
The House of Representatives panel accuses Mr Trump of an attempted coup.
The select committee has conducted a nearly yearlong investigation into how Trump supporters invaded Congress on 6 January 2021 to disrupt lawmakers as they certified Democrat Joe Biden's election victory.
On Tuesday, in the fourth public hearing so far, the panel heard from election workers in the states of Arizona and Georgia. Mr Biden defeated Mr Trump in both states, which had previously backed Republicans for the White House.
"We received... in excess of 20,000 emails and tens of thousands of voice mails and texts, which saturated our offices and we were unable to work, at least communicate," Mr Bowers, speaker of the Arizona House of Representatives, told the select committee.
The witness - who campaigned for Mr Trump in 2020 - said the threats and insults have continued with protesters outside his house attempting to smear him as a paedophile.
"It was disturbing, it was disturbing," Mr Bowers said, according to BBC.
He recalled Trump lawyer Rudy Giuliani at one point telling him: "We've got lots of theories, we just don't have the evidence."
The panel also heard testimony from Shaye Moss and her mother, Ruby Freeman, who became the targets of conspiracy theories in their jobs as election workers in Fulton County, Georgia.
Although Mr Biden won the state by nearly 12,000 votes, Mr Trump and his supporters spread unfounded claims of mass voter fraud.
In recorded messages, Mr Trump had called Ms Moss "a professional vote-scammer and hustler", alleging the mother-daughter duo cheated to help Democrats.
"I've lost my name, I've lost my reputation, I've lost my sense of security," Ms Freeman said through tears, in video presented by the committee on Tuesday.
"Do you know what it feels like to have the president of the United States target you?"
Ms Moss said she faced "a lot of threats wishing death upon me", and that the harassment - including racial abuse - had "turned my life upside down".
"I no longer give out my business card. I don't want anyone knowing my name."
Ms Moss said she is reluctant to go anywhere, including the supermarket, and has gained about 60lb (27kg) in weight, BBC reported.
She told the committee that Trump supporters had visited her grandmother's home, looking for her and hoping to make a "citizen's arrest".
Lawmakers also heard from Republican poll organisers in Georgia about their difficulty in stamping out conspiracies fanned by Mr Trump.
Gabriel Sterling, a top election official in Georgia, told the committee that fighting the election scam claims "was like a shovel trying to empty the ocean".
His boss - Georgia Secretary of State Brad Raffensperger, whom Mr Trump repeatedly pressed to "find" the votes he needed to win the state - ticked through a laundry list of allegations made by the Trump team in legal action against the state.
"In their lawsuits, they alleged 10,315 dead people [voted]," Mr Raffensperger said, but a thorough review found a total of only four.
The secretary said further investigation had debunked other claims about illegal votes by underage and non-registered voters, as well as convicts.
"We had many allegations and we investigated every single one of them."
The hearings have attempted to tie the former president directly to the efforts to overturn the election, according to BBC.
At Tuesday's hearing, the committee chairman Bennie Thompson, a Democrat, said: "A handful of election officials in several key states stood between Donald Trump and the upending of American democracy."
His deputy on the committee, Liz Cheney, a Republican, said: "We cannot let America become a nation of conspiracy theories and thug violence."