The escalation comes as Trump seeks to harden up his base while also laying the groundwork to challenge the election results yet again, with repeated calls for a vote that is "too big to rig."
Far fewer people use Truth Social than X, formerly Twitter, where Trump boasted a far louder voice before his supporters stormed the US Capitol and he was temporarily banned.
But the former president has posted relentlessly on his Truth site -- over 30 times per day in September, on average -- with sprees stretching late into the night.
The attacks on Harris included claims the vice president is "guilty of CRIMES" and "should be IMPEACHED, PROSECUTED, or BOTH."
Trump has also promised to punish other lawmakers and said if he wins in November, then voters, lawyers, donors and election officials who "CHEATED" in the 2020 or 2024 elections will be "prosecuted at levels, unfortunately, never seen before in our Country."
"Trump's base loves this nonsense," Larry Sabato, director of the University of Virginia's Center for Politics, told AFP. "Yet there are millions of others, perhaps on the edge of voting for him again, who might recoil."
"People should wake up every day and be forced to see and listen to his posts."
The Trump campaign did not respond to a request for comment.
- Pre-emptive fraud claims -
In between self-glorifying opinion polls, links to conservative media and posts hawking $100,000 watches and other merchandise, the former president's feed is full of erratic, often all-uppercase screeds that push the website's 1,000-character limit.
"WOMEN ARE POORER THAN THEY WERE FOUR YEARS AGO, ARE LESS HEALTHY THAN THEY WERE FOUR YEARS AGO, ARE LESS SAFE ON THE STREETS THAN THEY WERE FOUR YEARS AGO," Trump began one post that made false claims about abortion.
"I HATE TAYLOR SWIFT," he said in another, after the singer endorsed Harris.
With election day less than a month away, Trump has ramped up warnings of fraud and homed in aggressively on Harris -- notably blaming her for border crossings in misleading posts that AFP fact-checkers found were distorting data, some of which is decades old, about migrants with criminal convictions.
He has baselessly accused his opponent of illegally registering immigrants to vote and shared a manipulated video that falsely portrayed her asking them if they had done so.
Other insults have been personal, branding Harris as "crazy," "lyin'" and "cognitively challenged" and accusing her of staging photos and paying fake supporters.
"Did they give Comrade Kamala the questions?" he said after their debate. "It was 3-on-1, but they were mentally challenged people, against one person of extraordinary genius."
John Jost, a New York University professor of psychology and politics, said Trump's activity could signal "dread, immense anxiety and hatred" over the possibility of losing.
"Trump is a desperate man. He is willing to say or do anything, regardless of truth value."
- 'Twisted commentary' -
Facing backlash for amplifying an August post implying Harris exchanged sexual favors for political gain, Trump said on a podcast that "the ones you get in trouble with are the reposts."
Yet multiple times since, he has boosted conspiratorial and sometimes nakedly racist posts.
One from "@1776WeThePeople1776," an account promoting QAnon conspiracies, featured a picture of a knife-wielding man with a head covering. It said: "We're your new neighbors."
After Sean "Diddy" Combs was indicted, Trump shared an image -- which AFP fact-checkers determined was doctored -- of Harris with the rapper, from an account called "@akaPR0B0SS."
"Even to someone like me who has followed Trump for nine years, this is shocking," said Sabato. "For most of my life a candidate who had written this sort of twisted commentary would have been driven out of his nomination."
As Republicans including Trump baselessly accused Haitians in Ohio of eating pets, the former president promoted a misrepresented video and other dubious evidence online.
The community was then flooded with bomb threats.
Jared Holt, senior researcher of US extremist movements at the Institute for Strategic Dialogue, warned of Trump emboldening "the ugliest parts of the modern conservative movement."
"His social media posts encourage, normalize and spread extremist ideologies."
