By Sam CabralBBC News, Washington

With the spectre of criminal charges hanging over his third bid for the White House, Donald Trump has scheduled a massive rally in Texas this weekend.

The campaign event, planned for Saturday, marks the former president's return to a traditionally conservative state in which he remains very popular.

But his decision to hold the rally in Waco - best known for an armed standoff 30 years ago - has raised eyebrows.

The 1993 tragedy is seen as a landmark event for the American far-right.

A city of about 140,000 people in the heart of Texas, Waco is celebrated these days as host to Baylor University, the Dr Pepper Museum and the home-improvement reality show Fixer Upper.

Three decades ago, however, it was where FBI agents, the US military and Texas law enforcement laid siege to a religious cult known as the Branch Davidians.

The small, insular Christian sect was led at the time by David Koresh, 33, an apocalyptic prophet who allegedly believed he was the only person who could interpret the Bible's true meaning.

Under Koresh, the Branch Davidians had stockpiled weapons in order to become an "Army of God".

Authorities intended to conduct a surprise daylight raid on 28 February 1993 and arrest Koresh, but what ensued was a 51-day standoff that left 76 people dead, including more than 20 children and four federal agents.

The calamity - and a similar incident one year earlier in Ruby Ridge, Idaho - tapped into a vein of anti-government sentiment often linked to the rise of far-right militia groups in the US through the mid-1990s and early 2000s.

"The events at Waco have taken on a life of their own in anti-government and white supremacist circles," said Heidi Beirich, co-founder of the Global Project Against Hate and Extremism non-profit.

"[They've] taken up the cause that this was an out-of-control government ... that citizens couldn't live the lives they wanted and the federal government came barrelling in and burned them out of their facilities."

Two years after the siege, Timothy McVeigh - a young man who had shown his support at Waco and became fixated with the federal response as evidence of an impending New World Order - bombed a federal building in Oklahoma City, Oklahoma, killing 168 people and injuring nearly 700 others. It remains the deadliest act of domestic terrorism in US history.

The raid also had an impact on conspiracy theorist Alex Jones, who - as a young radio host in 1998 - organised a campaign to rebuild the Branch Davidians' chapel as a memorial to those who had died. Mr Jones was among the most prominent early voices to back Mr Trump in his 2016 presidential campaign.

"Waco still resonates in this anti-government space as something that shows the federal government doesn't protect people, is out to violate their civil rights, is out to take their guns," Ms Beirich said.

"Nowadays that very much feeds into the 'deep state' conspiracies that we see on the far-right; the attacks on the FBI; the idea that federal law enforcement is a weapon of Democratic presidents."

Mr Trump has often drawn on these frustrations, painting himself as the victim of a secret cabal of government operatives and effectively tearing down the walls that separated the mainstream Republican Party from its more extremist and radical fringes.

The former president's sense of victimhood has only intensified since he left office. His conspiracies about the 2020 election still abound and he has framed the legal action he is facing on multiple fronts as an effort to destroy him.

On his Truth Social platform on Friday, Mr Trump warned an indictment risked "potential death and destruction" that could be "catastrophic" for the nation.

Shortly after that post, an envelope containing white powder and a threatening message was delivered to the office of Alvin Bragg, the Manhattan district attorney investigating Mr Trump's hush-money payment to a pornographic actress. According to BBC News US media partner CBS News, the typewritten note said: "Alvin. I am going to kill you."

Saturday's event will fall during the 30th anniversary of the standoff between Koresh's "army" and the government.

"It's hard for me to believe that he doesn't know what he's doing," Ms Beirich told the BBC, adding Trump "has the ability to motivate supporters to engage in very extreme behaviour".

The Houston Chronicle - Texas' largest and most-read newspaper - reported this week that the Trump campaign is calling the visit "purely coincidental".

But in a column on Thursday, the paper's editorial board laid bare an accusation: "Trump is stoking the fires of Waco."

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