WASHINGTON — Representative Liz Cheney of Wyoming, the onetime Republican leader ousted from her post and pushed to the sidelines by her own party for bluntly condemning former President Donald J. Trump’s false election claims, has re-emerged as a force on Capitol Hill — this time as one of the most active and aggressive members of the special committee investigating the Jan. 6 attack.

Ms. Cheney’s no-holds-barred style grabbed the spotlight this week as the committee led the charge to hold Mark Meadows, the former White House chief of staff, in contempt for his refusal to cooperate with the panel’s investigation.

Twice in the space of two days, from hearing rooms on Capitol Hill, she read aloud panicked and angry text messages that Republican lawmakers sent Mr. Meadows on Jan. 6 as rioters laid siege to the complex.

“It’s really bad up here on the Hill,” one wrote in a text that Ms. Cheney read on Tuesday, ahead of a House vote to hold Mr. Meadows in contempt. “The president needs to stop this ASAP,” another said. A third simply wrote: “Fix this now.”

Ms. Cheney’s recitation — delivered in her signature monotone — reflected her approach as the vice chairwoman of the panel, where she is serving in defiance of Republican leaders who have sought to thwart the investigation at every turn.

Both in public and behind the scenes, Ms. Cheney has used her perch to hold up an unsparing and often unflattering mirror to her own party, exposing Republicans’ complicity in the stolen-election narrative that fueled the Jan. 6 riot. She has done so even in the face of a primary challenge from a Trump-backed candidate that is likely to be a referendum on the former president.

“For her, this is about setting out in stark relief what the truth is, and in some way making the Republican Party confront that truth,” said Michael Steele, a former chairman of the Republican National Committee. “‘Here are the text messages, here are the phone logs, here are the conversations.’ That becomes a very difficult story line to refute.”

Ms. Cheney, the scion of a conservative dynasty, has found herself in an unusual place as a result of her position on the committee, as has the panel’s only other Republican member, Representative Adam Kinzinger of Illinois. They have been ostracized and derided as grandstanders by their own party; at the same time, they have been embraced by Democrats as the only Republicans willing to demand a full and bipartisan accounting of the worst attack on Congress in centuries.

During committee hearings and floor debates, Ms. Cheney often tailors her public comments to an audience of Republican voters and elected officials. On Monday, she chose to publicly read anguished texts sent to Mr. Meadows on Jan. 6 by conservative personalities like the Fox News host Laura Ingraham and Mr. Trump’s son Donald Trump Jr.

In doing so, Ms. Cheney made the case that there was a moment when even the most devoted loyalists to Mr. Trump understood that his inaction in the face of the violence at the Capitol was inexcusable.

“We as Republicans used to be unified on this point — in terms of what happened on Jan. 6 and the responsibility the president had to stop it,” Ms. Cheney said.

But her challenge is that her audience is a decidedly hostile one, a reality that is perhaps nowhere clearer than at home in Wyoming, where she has been purged from the state party and is facing a challenge from Harriet Hageman, a Never Trumper turned MAGA acolyte.

“By pointing out the facts of what happened Jan. 6, and the hypocrisy of those pushing a narrative into a population willing to receive it, she’s identifying the lies,” said Denver Riggleman, a former Republican congressman who is on the special committee’s staff. “And hoping that a small percentage will see this and understand that Jan. 6 not only was one of the worst things in our history, in our capital, but has also been used to play people for money.”

Behind the scenes, Ms. Cheney has been just as aggressive. She is known to draft her own remarks in advance of hearings and does her own preparation work, poring over the voluminous documents the committee has obtained. She also pressed to assemble a team of former intelligence analysts and law enforcement specialists on the committee’s staff, some of them Republicans — a move that bolstered the committee’s bipartisan bona fides.

In closed-door interviews held in a nondescript federal office building near the Capitol, Ms. Cheney has emerged as a leader and central figure on the panel, known for drilling down into the details of the assignment she views as the most important of her political career. She is well-versed in the criminal code and often uses language borrowed from it to make clear she believes the former president and others face criminal exposure.

She has been particularly pointed in suggesting that Mr. Trump, by failing to stop the violence at the Capitol on Jan. 6, may have violated a federal law that prohibits obstructing an official proceeding before Congress.

“We know hours passed with no action by the president to defend the Congress of the United States from an assault while we were trying to count electoral votes,” Ms. Cheney said. “Mr. Meadows’s testimony will bear on a key question in front of this committee: Did Donald Trump, through action or inaction, corruptly seek to obstruct or impede Congress’s official proceeding to count electoral votes?”

The statute that Ms. Cheney was citing is the basis for the main charge that law enforcement officials have brought against more than 200 Capitol rioters accused of interfering with Congress’s role in certifying the Electoral College vote. The obstruction law, which prosecutors have used in lieu of sedition or insurrection, is how the government has chosen to describe the central political crime of Jan. 6: disrupting the peaceful transition of power.

Ms. Cheney has also established herself as a tough and meticulous questioner in deposition interviews.

When Jeffrey Clark, a Justice Department lawyer who participated in Mr. Trump’s frenzied efforts to overturn the election, appeared before the committee last month, Ms. Cheney pressed him in a series of rapid-fire questions on various aspects of the plan to keep Mr. Trump in power.

“In terms of your assertions about Dominion voting machines and smart thermostats, could you explain where you got that information?” she asked about a wild conspiracy theory about the hacking of voting machines that was endorsed by Trump supporters.

Ms. Cheney has taken particular interest in holding members of her own party accountable.

“I’d like to ask the witness when he first met Congressman Scott Perry,” Ms. Cheney asked Mr. Clark, referring to a lawmaker who had acted as a conduit between him and Mr. Trump.

“Did you have any interaction with any other members of Congress?” she asked at another point.

Each time Mr. Clark refused to answer.

“I just want to be clear that I want the record to show that Mr. Clark is refusing to answer any questions, including those questions that have nothing to do with any of his interaction with the president, questions that couldn’t conceivably be covered by any assertion of executive privilege,” Ms. Cheney said.

Ms. Cheney has said that the investigation could very well lead to Mr. Trump facing her questions, with criminal penalties hanging over his head if he lies.

“Any communication Mr. Trump has with this committee will be under oath,” Ms. Cheney said this month. “And if he persists in lying then, he will be accountable under the laws of this great nation and subject to criminal penalties for every false word he speaks.”

Alan Feuer contributed reporting.