Suspect Tries to Compare Capitol Riot to Last Year’s Violence in Portland, Ore.

The reason, Mr. Broden said, was politics.

“Most, if not all, of the Portland dismissals, offers of pretrial diversion, and pleas to significantly reduced charges came after a change from the Republican administration to the Democratic administration running the Department of Justice,” he wrote.

Prosecutors disputed Mr. Broden’s calculations as a preliminary matter, arguing that they contained “inaccuracies,” but the government’s filing also sought to make a broader point that there was more at stake in Washington on Jan. 6 than in weeks of turmoil in Portland.

Mr. Miller, prosecutors noted, was “part of a mob” that “breached the Capitol building, and assaulted law enforcement with the goal of impeding congressional certification of the 2020 presidential election.” The defendants in Portland, they pointed out, never actually broke into the courthouse and never disrupted a proceeding before Congress.

The prosecutors also argued that they have better evidence against Mr. Miller — and the hundreds of other rioters charged in connection with Jan. 6 — than they ever managed to obtain against the protesters in Portland.

In the days leading to the Capitol attack, court papers say, Mr. Miller posted messages on Facebook, talking about a potential civil war and the collapse of the economy, and suggesting that he might take firearms to Washington. On the day of the riot, the papers say, surveillance videos show him pushing past officers and entering the Capitol while others show him confronting the police inside in “a fighting stance with one of his legs in front of the other.”

Moreover, prosecutors say, in the days that followed the riot, Mr. Miller posted messages on Twitter threatening to “assassinate” Representative Alexandria Ocasio-Cortez, Democrat of New York. He is also accused of threatening the officer who fatally shot a woman, Ashli Babbit, in the Capitol by posting a photo of a noose on Instagram and writing, “He will swing.”