G.O.P. lawmakers in the state are calling for the resignation of a legislator who appears to have encouraged protesters to breach the State Capitol in December.A little more than two weeks before a mob of supporters of Donald J. Trump stormed the U.S. Capitol, falsely claiming that he had won the election, a strikingly similar event had unfolded on the other side of the country, at the State Capitol in Oregon.There, in December, a restive crowd had breached the exterior doors and battled law enforcement officers in a building that is capped by a gold-leaf pioneer wielding an ax. The agitators, waving Trump flags and clad in body armor, wielded pepper spray and smashed windows. “Arrest Kate Brown!” the crowd chanted, referring to the state’s Democratic governor.Republicans in Congress have resisted a full, formal investigation into the much larger attack by protesters on the U.S. Capitol on Jan. 6, but in Oregon, lawmakers facing new evidence about the Dec. 21 siege in Salem are taking a different approach. On Monday, the state’s House Republican caucus signed a letter encouraging the resignation of a colleague, Representative Mike Nearman, who in a newly discovered video appeared to be coaching protesters on how they might gain access to the building.The House Republican leader, Christine Drazan, said on Tuesday that she believed there was enough support in her caucus to expel Mr. Nearman from the State Legislature if he did not resign. Legislators in the state have never before expelled one of their own.“I would hope that Representative Nearman would make the decision to not be the first,” Ms. Drazan said in an interview.The protest in Salem was part of a series of demonstrations that broke out across the country after the Nov. 3 election as supporters egged on by Mr. Trump mobilized to contest an election they falsely believed had been stolen. Some of the protests targeted state leaders who had imposed lockdowns and mask orders to counter the coronavirus pandemic.In Salem on Dec. 21, dozens of people mobilized outside the Capitol, expressing frustration that the building had been closed to the public amid the pandemic. Carrying signs condemning the “lying lockdown” and shouting, “Let us in,” some in the crowd surged through an open door on the building’s north side before law enforcement officers moved to confront them.A larger crowd later managed to push in through the doorway but, facing a line of officers in riot gear, they did not reach the rotunda area or areas of the building where legislators were working. Officers later made some arrests and cleared the building.In the months since the breach, videos have made it clear that the crowd had assistance from someone on the inside. Security footage made public days afterward showed Mr. Nearman, who has represented a district that lies south and west of Salem for the past six years, opening a door in a way that allowed protesters inside as he left the building. Mr. Nearman, who walked around the building and re-entered it, faces misdemeanor charges of official misconduct and criminal trespass.After the first video emerged, Mr. Nearman said he did not condone violence but also said he believed that legislative proceedings should be open to the public.Then last week, new footage surfaced, suggesting not only that he may have expected protesters to enter the building, but that he had offered to help them. The video, earlier reported by Oregon Public Broadcasting, appeared to be streamed online a few days before the December intrusion. It showed Mr. Nearman making public remarks in which he coyly gives out his own cellphone number with a suggestion that anyone who might need to enter the Capitol building could text him if they needed a way inside. He referred to the idea as “Operation Hall Pass.”“That is just random numbers that I spewed out. That’s not anybody’s actual cellphone,” Mr. Nearman said after giving out his cell number. “And if you say, ‘I’m at the West entrance’ during the session and text to that number there, that somebody might exit that door while you’re standing there. But I don’t know anything about that.”Barbara Smith Warner, a Democratic lawmaker from Portland who is the House majority leader, said she found it hard to believe that a sitting legislator would put everyone in the building at risk, not only by intentionally opening the door but by doing it in a premeditated way.“That is mind-boggling,” Ms. Smith Warner said. “If that’s not traitorous, I don’t know what is.”Mr. Nearman did not respond to messages seeking comment. In an interview with the conservative radio host Lars Larson, Mr. Nearman said he had been “clowning around” in the video and “setting up” for what he had assumed would be a peaceful protest. He said he had been speaking in the video to a group that was not known to be violent.“I’m willing to have some consequences for what I did, or whatever, but this is super extreme,” Mr. Nearman said.Ms. Smith Warner said she came to see the Dec. 21 siege as a kind of dress rehearsal for what happened in the nation’s Capitol a few weeks later, with the same types of grievances on display. While Republican legislators in Oregon had been largely silent about the December siege until now, she said, she applauded those who were now willing to take on the issue.“I don’t want to minimize that at least some of the Republicans here are doing the right thing,” Ms. Smith Warner said. “That is no small thing. I do think their base will consider that a betrayal.”The U.S. House voted in May to create an independent commission to investigate the Jan. 6 assault on the U.S. Capitol, which left several people dead, injured law enforcement officers and had lawmakers fleeing for safety as a mob ransacked the complex. But that plan for a broader accounting of the day was stalled by Republicans in the Senate who appeared to fear the political consequences of an open-ended inquiry.In Oregon, House Speaker Tina Kotek announced that a bipartisan special committee would convene this week to consider whether Mr. Nearman should be expelled. Ms. Drazan, the Republican leader, said she believed that the matter should have been handled by a different committee but supported the idea of considering expulsion.If a resolution to expel goes to the full House, it would need 40 of the chamber’s 60 lawmakers to approve it. The chamber has 37 Democrats.Ms. Drazan said she did not see much of a parallel between the siege in Washington and the one in Salem, and said she preferred to keep her focus on events in Oregon rather than weighing in on how Republicans in Congress should handle the Jan. 6 events. She said she hoped Republican lawmakers would be as focused on doing the right thing in their own party as they have been on criticizing the opposing party.“I am just exhausted by national politics,” Ms. Drazan said. “They just need to get their act together. They need to start to serve the greater good.”Ms. Drazan noted that when Republican Party leadership in Oregon passed a resolution that embraced the unfounded conspiracy theory that the Jan. 6 attack was a left-wing “false flag” plot to frame Mr. Trump’s supporters, her caucus in the Legislature disavowed the resolution, declaring that there was no evidence of a false flag effort and that the election was over.“We have, I hope, a clear-minded view of what is public service and what is not,” Ms. Drazan said.Mr. Nearman was among those who signed the letter. More