COLLEGE PARK, MD. -- In a text message, a radicalized Donald Trump supporter suggested getting a boat to ferry "heavy weapons" across the Potomac River into the waiting arms of their members in time for Jan. 6, court papers say.

It wasn't just idle talk, authorities say. Investigators found invoices for more than US$750 worth of live ammunition and for a firearm designed to look like a cellphone at the Virginia home of Thomas Caldwell, who's charged with conspiring with members of the far-right Oath Keepers militia group in one of the most sinister plots in the U.S. Capitol siege.

Right-wing extremists, blessed by Donald Trump, were unleashed last month, and their menacing presence has reignited the debate over domestic extremism and how law enforcement should be handling these groups.

Their talk of civil war, traitors and revolution mirrored fighting words echoed by right-wing social media personalities and websites for months as Trump spread bogus claims about a rigged presidential election.

In nearly half of the more than 200 federal cases stemming from the attack on the Capitol, authorities have cited evidence that an insurrectionist appeared to be inspired by conspiracy theories or extremist ideologies, according to an Associated Press review of court records.

The FBI has linked at least 40 defendants to extremist groups or movements, including at least 16 members or associates of the neo-fascist Proud Boys and at least five connected to the anti-government Oath Keepers. FBI agents also explicitly tied at least 10 defendants to QAnon, a pro-Trump conspiracy theory that has grown beyond its fringe origins to penetrate mainstream Republican politics.

In at least 59 other cases, authorities link defendants to violent or extremist rhetoric, conspiracy theories or other far-right connections on social media and other forums before, during or after the Jan. 6 siege, a deeper review by the AP found.

The AP's review found that in many of those cases the defendants repeated false claims, made by Trump for months of his presidency, that the U.S. election was rigged. Some broadcast death threats at Democrats on their social media accounts or in messages. Others were deeply entwined in a world of far-right conspiracy theories about the COVID-19 pandemic. And dozens of the alleged rioters echoed words used by QAnon supporters, who push a baseless belief that Trump is a secret warrior fighting to expose a cabal of Satan-worshipping bureaucrats and celebrities who traffic children.

On Saturday, the Senate acquitted Trump in his second impeachment trial. A leading liberal advocacy group is urging its supporters to call on attorney general nominee Merrick Garland to "investigate and prosecute Trump and his entire criminal network for law breaking."

The U.S. attorney's office in Washington has assigned a special task force of prosecutors examining whether to bring sedition charges against some of the rioters, as prosecutors and federal agents across the country develop more cases against extremists who plotted to attack the Capitol. Prosecutors have another task force examining attacks targeting journalists.

U.S. President Joe Biden, in office not yet a month, has already ordered law enforcement and intelligence officials to investigate domestic terrorism. But increased enforcement is not so simple. Much of the inflammatory rhetoric is protected by the First Amendment.

And some civil rights groups have expressed hesitation over any expansion by law enforcement, because Black and Latino communities have born the brunt of security scrutiny and they fear new tools to target extremism will end up tracking them.

Meanwhile, conspiracy theories proliferate. Conservative social media app Parler doubled its userbase, adding 8.7 million users, after the election when Facebook and Twitter cracked down on accounts spreading misinformation about the election.

Calls on the conservative platform for users to revolt or launch a war over the election results also grew, according to the AP's analysis of an archived Parler dataset of 183 million posts and 13 million user profiles.

The archive, which was captured between August 2018 and Jan. 10, when Parler was taken offline, was provided in advance of publication to the AP by researcher Max Aliapoulios at New York University.

Parler posts containing the word "revolution" grew by five times as much as the overall rate of message traffic after the election, the analysis found.

About 84% of posts referring to the hashtag #1776 occurred on or after Election Day, according to AP's analysis. Post-election references to "treason" and the QAnon slogan "trust the plan" both increased by about 10 times the overall rate, the data showed.

From Jan. 6 through Jan. 8 the terms "civil war," "trust the plan" and "hold the line" were mentioned more than 250,000 times across online media, including Twitter, Redditt and Instagram, according to an analysis by media intelligence firm Zignal Labs.

As well, Trump supporters who flooded the Capitol were quick to co-opt lingo from the American Revolution and the nation's founding documents to paint themselves as patriots instead of extremists. In the federal cases, the FBI quotes at least 11 defendants referring to "we the people," at least 10 referring to "1776," at least nine using "revolution" and at least eight using some variation of "traitor" or "treason."

"Everybody in there is a treasonous traitor," defendant Peter Stager, a resident of Arkansas, said of the Capitol, on a video posted on Twitter. "Death is the only remedy for what's in that building." A lawyer for Stager did not respond to a request for comment.

A Georgia lawyer's Parler posts became increasingly paranoid and angry after the presidential election began to shift to Biden's favour. William Calhoun of Americus, Georgia, posted about storming the Capitol on the eve of the insurrection, warned of an impending "civil war" and threatened to "slaughter" Democrats.

"For my part, I'll be slinging enough hot lead to stack you commies up like cordwood," he wrote.

Calhoun returned home after the siege and resumed representing clients at court hearings. Federal agents say he had at least two rifles, four shotguns, a pistol and hundreds of rounds of ammunition in his possession when they arrested him. A magistrate judge ordered Calhoun detained in custody. His lawyer had no comment.

The Oath Keepers prepared in the weeks leading up to Jan. 6 as if they were going to war, investigators say. One advised another extremist to be "fighting fit" by the inauguration and discussed holding "2 days of wargames" as part of a larger "combat" training for "urban warfare, riot control, and rescue operations," according to court papers.

A judge late last week ruled against releasing Caldwell, who authorities say conspired with members of the Oath Keepers to undo Biden's victory. In urging the judge to keep Caldwell locked up, the prosecutor said authorities found a "death list" at his Virginia home with the name of an election official in another state who gained notoriety around the presidential election.

Caldwell's lawyer said prosecutors have no evidence that his client, who denies being a member of the Oath Keepers, ever entered the Capitol. He called the indictment "imaginative."

"These things were taken out of context!" Caldwell interjected at the hearing.

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Seitz reported from Chicago. Associated Press data journalist Larry Fenn in New York and AP writers Alanna Durkin Richer in Boston and Garance Burke in San Francisco contributed to this report.