Ali Alexander, a prominent organizer of the Stop the Steal rally that drew supporters of President Donald J. Trump to Washington on Jan. 6, plans on Thursday to tell the House committee investigating the attack on the Capitol that he had “nothing to do with any violence or lawbreaking” that day, according to a copy of his opening statement obtained by The New York Times.

“Anyone who suggests I had anything to do with the unlawful activities on Jan. 6 is wrong,” Mr. Alexander, who pledged to supply the committee with voluminous documents, plans to say in a deposition. “They’re either mistaken or lying.”

Mr. Alexander, a provocateur who rose in right-wing circles in the chaotic aftermath of the 2020 presidential election, was one of a handful of planners who put together marches and rallies around the country protesting the outcome, culminating with the one in Washington on Jan. 6 that brought together throngs of attendees who went on to violently storm the Capitol.

He attended Mr. Trump’s incendiary speech at the Ellipse near the White House that day, then marched with the crowd toward the Capitol, along with the conspiracy theorist Alex Jones of Infowars and the young white nationalist Nicholas J. Fuentes, arriving, as he put it in his prepared remarks to the panel, “in the early stages of the lawbreaking.”

Late last month, the House committee issued subpoenas for both Mr. Alexander and Mr. Jones, suggesting that they might have knowledge of how the Stop the Steal rallies on Jan. 6 came together.

“We need to know who organized, planned, paid for and received funds related to those events, as well as what communications organizers had with officials in the White House and Congress,” Representative Bennie Thompson, Democrat of Mississippi and the committee chairman, said at the time.

The panel is seeking information from Mr. Alexander about his connections with members of Congress and his repeated use of violent language, members said.

In the weeks before the attack, Mr. Alexander repeatedly referred during Stop the Steal events to the possible use of violence to achieve the organization’s goals, and he claimed to have been in communication with the White House and members of Congress about events planned to undermine the official count by Congress of the Electoral College results, the committee said.

Mr. Alexander has said that he, along with Representatives Mo Brooks of Alabama, Paul Gosar of Arizona and Andy Biggs of Arizona, all Republicans, set the events of Jan. 6 in motion.

“We four schemed up of putting maximum pressure on Congress while they were voting,” Mr. Alexander said in a since-deleted video posted online, “so that who we couldn’t lobby, we could change the hearts and the minds of Republicans who were in that body, hearing our loud roar from outside.”

In his opening statement to the committee, Mr. Alexander plans to give a flavor of his personal biography — his mother was Black and lived in public housing; his father, an Arab, disappeared from his life at a young age — and to suggest that he has become a target for those looking to blame the violence of Jan. 6 on someone.

“It is not uncommon in the aftermath of historic chaos and disruption to look for a bogeyman,” his opening statement says. “After all, someone must be held accountable, right?”

Mr. Alexander also intends to describe some of the bitter rivalries that divided the small group of planners that put together large pro-Trump events in Washington in November, December and January.

According to the prepared statement, he plans to say that he sought to “de-escalate events at the Capitol” on Jan. 6 while other organizers, including Amy Kremer and her daughter Kylie Kremer, who ran a group called Women for America First, “weren’t working with police” to quell the crowd.

In the past few weeks, Mr. Alexander claims to have spent more than 100 hours searching his archives for “relevant and responsive documentation to this committee’s requests,” according to his statement. He says that he has hired “attorneys and computer consultants to be as responsive as possible.”

Mr. Alexander’s cooperation comes as the committee is considering a criminal contempt of Congress referral against a third recalcitrant witness, Mark Meadows, who served as Mr. Trump’s White House chief of staff.

Mr. Meadows, who has turned over thousands of pages of documents to the committee, informed the panel Tuesday that he was no longer willing to sit for an interview with its investigators at a scheduled deposition Wednesday, reversing a deal he reached with the panel just last week to attend an interview. The leaders of the committee immediately threatened to charge Mr. Meadows, a former congressman from North Carolina, with contempt of Congress if he did not appear.

In a letter sent to Mr. Meadows’s lawyer on Tuesday evening, Mr. Thompson said Mr. Meadows had provided some useful information to the committee, including a November email that discussed appointing an alternate slate of electors to keep Mr. Trump in power and a Jan. 5 message concerning putting the National Guard on standby.

Mr. Meadows also turned over to the committee text messages with a member of Congress in which the member acknowledged a plan to object to Mr. Biden’s victory would be “highly controversial” to which Mr. Meadows responded, “I love it,” and other exchanges about the need for the former president to issue a public statement attempting to stop the mob as violence consumed the Capitol on Jan. 6.

But Mr. Meadows also informed the committee he had turned in his cellphone used on Jan. 6 to his service provider, and he was withholding some 1,000 text messages connected with the device, prompting many questions and the need for more cooperation and a deposition, Mr. Thompson said.

“The select committee is left with no choice but to advance contempt proceedings and recommend that the body in which Mr. Meadows once served refer him for criminal prosecution,” he wrote.

The committee recently sent a flurry of subpoenas to telecommunications companies seeking the data of dozens of individuals, including Mr. Meadows, prompting his lawyer to object to a request he said sought “intensely personal communications” with no relevance to any legitimate investigation.

The subpoenas, which follow records preservation demands sent to 35 technology and social media companies in August, do not seek the content of any communications but simply the dates and times of when the calls and messages took place, according to a committee aide.

The committee has now interviewed more than 275 witnesses and is receiving cooperation from some members of former Vice President Mike Pence’s inner circle, including Marc Short, his former chief of staff.

But several high-profile witnesses are stonewalling the panel, in line with a directive from Mr. Trump. The former president is battling in court to block the release of documents requested by the committee that he says are subject to executive privilege, though the Biden administration has refused to assert the claim.

The House voted in October to recommend that another of Mr. Trump’s associates, Stephen K. Bannon, be charged with criminal contempt of Congress for refusing to cooperate. A federal grand jury subsequently indicted him on two counts that could carry a total of up to two years behind bars. A judge on Tuesday set a July 18 trial date for Mr. Bannon, meaning that the select committee will most likely have to wait the better part of a year, if not longer, for a resolution of his case and any potential cooperation from him.

The committee has also recommended contempt charge against Jeffrey Clark, a former Justice Department lawyer who participated in Mr. Trump’s efforts to invalidate the 2020 election results, for refusing to cooperate with its inquiry. The panel is waiting to complete that referral until it can determine how much information Mr. Clark is willing to provide during a deposition scheduled for Dec. 16. Mr. Clark has said he will invoke his Fifth Amendment right against self-incrimination.

Another potential witness, John Eastman, a lawyer who wrote a memo that some in both parties liken to a blueprint for a coup to keep Mr. Trump in power, has also indicated that he plans to invoke the Fifth Amendment in response to the committee’s subpoena.

A third witness, the political operative Roger J. Stone Jr., told the committee this week that he, too, planned to invoke his right against self-incrimination in defying a subpoena, declining to sit for an interview or produce documents.