Oath Keepers leader Stewart Rhodes, staring down an 18-year prison sentence for seditious conspiracy in the Jan. 6, 2021, attack on the U.S. Capitol, said his trial laid out a blueprint for how special counsel Jack Smith will convict former President Donald Trump.

Rhodes, a Yale Law School graduate and former Army paratrooper who founded the Oath Keepers militia group in 2009, said the federal government is working to turn Mr. Trump’s inner circle against him and scare off potential witnesses for the former president’s defense.

“They’re going to do the same thing to President Trump that they did to me,” Rhodes told The Washington Times from the D.C. Department of Corrections Central Detention Facility, where he is kept in isolation.

He sent a grave warning to Mr. Trump: “You’re going to get railroaded. You’re going to be found guilty if you try to go to trial. So everyone’s been demoralized and more likely to take a plea deal and agree to ‘test-a-lie’ against President Trump.”

Rhodes stressed that prosecutors used his words, not his actions, to convict him of seditious conspiracy — one step below treason.

“I didn’t enter the Capitol, but I was still found guilty by a D.C. jury of obstructing an official proceeding even though I didn’t even go inside,” he said. “And I was found guilty of seditious conspiracy, although they had zero evidence of an actual plan. They just used my speech. It will be the same thing with President Trump.”

He said federal prosecutors pressured members of the Oath Keepers to testify against him and four others in the militia who were convicted of seditious conspiracy and sentenced to prison terms of 36 to 54 months.

“They threatened [witnesses] with life in prison,” said Rhodes. “That’s what’s going to happen to President Trump.”

Rhodes predicted that Mr. Trump would face a left-leaning judge and jury in the District of Columbia just like the other convicted Jan. 6 defendants.

Mr. Trump’s legal team and campaign did not respond to a request for comment.

Mr. Trump is already facing a 37-count federal indictment for retaining and refusing to hand over classified documents from his office and residence at his private Mar-a-Lago club in Palm Beach, Florida. That case is being heard in federal court in Florida.

Mr. Smith is also investigating Mr. Trump’s attempt to overturn the 2020 presidential election results and his role in the riot at the Capitol. He is thought to be quietly working with a grand jury in the District.

Rhodes said prosecutors’ playbook opened with civil litigation to create the narrative of a coup plot. It started with a lawsuit brought by Rep. Bennie Thompson, the Mississippi Democrat who later led a House investigative committee, and 10 other House Democrats accusing Mr. Trump, Trump attorney Rudolph W. Giuliani, the Oath Keepers and another militia group, the Proud Boys, of illegally conspiring to incite the riot.

They sued under the Ku Klux Klan Act of 1871, a post-Civil War law that prohibits conspiracy to stop members of Congress from discharging the duties of their office.

The 32-page complaint filed in federal court in the District reads: “As part of this unified plan to prevent the counting of Electoral College votes, defendants Proud Boys and Oath Keepers, through their leadership, acted in concert to spearhead the assault on the Capitol while the angry mob that defendants Trump and Giuliani incited descended on the Capitol.

“The carefully orchestrated series of events that unfolded at the ‘Save America’ rally and the storming of the Capitol was no accident or coincidence. It was the intended and foreseeable culmination of a carefully coordinated campaign to interfere with the legal process required to confirm the tally of votes cast in the Electoral College,” the lawsuit said.

The court battle continues.

“The narrative has been set,” Rhodes said about the cases that landed before U.S. District Court Judge Amit P. Mehta —  the same judge who heard Jan. 6 criminal cases.

“The civil cases are the obvious narrative setting and the precursor to the criminal cases. The criminal cases are only meant to make it all true,” he said.

The Justice Department won seditious conspiracy convictions against Rhodes and Oath Keepers’ Florida chapter leader Kelly Meggs in November after a two-month federal trial in the District. Judge Mehta presided.

The jury found that both men planned for weeks to use force to keep Mr. Trump in the White House after he lost the 2020 election.

Rhodes was sentenced to 18 years in prison, followed by three years of supervised release. His is the longest sentence handed down for the assault on the Capitol. He is seeking new counsel to appeal his conviction.

Federal prosecutors have charged 11 people with seditious conspiracy related to the attack. They secured convictions or guilty pleas in eight cases and convicted three others of lesser but serious felony charges.

The seditious conspiracy law was adopted after the Civil War to be used against Confederates who continued to rebel against the U.S. government. These cases were brought infrequently and were often hard to prove, specifically when an alleged plot failed.

To win a seditious conspiracy case, the government must prove that two or more people conspired to “overthrow, put down or to destroy by force” the U.S. government or bring war against it or that they plotted to use force to oppose the authority of the government or to block the execution of a law.

It is insufficient to show that the defendants advocated using force. Prosecutors must show that they conspired to use force. A conviction carries up to 20 years in prison.