Democrats are launching their investigation into the Jan. 6 Capitol insurrection Tuesday with a focus on the law enforcement officers who were attacked and beaten as the rioters broke into the building –an effort to put a face on the violence that took place that day.

The police officers who are scheduled to testify endured some of the worst of the brutality. They were punched, trampled, crushed and sprayed with chemical irritants. They were called racial slurs and threatened with their own weapons as the mob of then-President Donald Trump’s supporters overwhelmed them, broke through windows and doors and interrupted the certification of Democrat Joe Biden’s presidential win.

"We’re going to tell this story from the beginning," said Maryland Rep. Jamie Raskin, a Democrat who sits on the new House panel that is investigating the attack. "The moral center of gravity is these officers who put their lives on the line for us."

Testifying will be Capitol Police officers Harry Dunn and Aquilino Gonell and Metropolitan Police officers Michael Fanone and Daniel Hodges. In previous interviews, Dunn has said that attackers yelled racial slurs and fought him in what resembled hand-to-hand combat as he held them back. Gonell, an Iraq veteran, detailed surgery on his foot and injuries from which he struggled to recover. Fanone has described being dragged down the Capitol steps by rioters who shocked him with a stun gun and beat him. Hodges was beaten and crushed between two doors, and his bloody face and anguished screams were caught on video.

The panel’s first hearing comes as partisan tensions have only worsened since the insurrection, with many Republicans playing down, or outright denying, the violence that occurred and denouncing the Democratic-led investigation as politically motivated. Democrats now want to launch the probe – and win public support for it – by reminding people how brutal it was, and how the law enforcement officers who were sworn to protect the Capitol suffered grave injuries at the hands of the rioters.

"What we really want to try to communicate during the hearing is what it was like to be on the front lines for these brave police officers," said House Intelligence Committee Chairman Adam Schiff, another member of the panel. "How vastly outnumbered they were, how well militarized the members of the crowd were."

The hope, Schiff said, is to "inform the public of what really happened that day, particularly in light of the efforts to whitewash that part of our history now."

The chairperson of the committee, Mississippi Rep. Bennie Thompson, says the hearing will "set the tone" of the probe, which will examine not only Trump’s role in the insurrection but the right-wing groups involved in coordination before the attack, white supremacists among them. It will also look at the security failures that allowed hundreds of people to breach the Capitol and send lawmakers running for their lives.

Some of those who broke in were calling for the deaths of House Speaker Nancy Pelosi and then-Vice President Mike Pence, who was hiding just feet away from the mob. Wyoming Rep. Liz Cheney, one of two Republicans on the panel, will give opening remarks after Thompson – an effort by Democrats to appear as bipartisan as possible.

The House Republican leader, Kevin McCarthy, withdrew the participation of other Republicans last week after Pelosi rejected two of them, saying their "antics" in support of Trump, and his lies that he won the election, weren’t appropriate for the serious investigation.

Monday evening, the House voted against a resolution offered by the GOP leader to force the members to sit on the panel. McCarthy has stayed close to Trump since the insurrection and has threatened to pull committee assignments from any Republican who participates on the Jan. 6 panel.

On Monday, he called Cheney and Illinois Rep. Adam Kinzinger, who is also sitting on the committee, "Pelosi Republicans," an effort that Cheney immediately called "childish."

"This is certainly not the time for name calling," Cheney told ABC's "Good Morning America" on Tuesday. "Those engaging in that just demonstrate yet again they don’t understand, they don’t care about or they are trying to obstruct this investigation into what happened."

In response to a question, Cheney said it was possible that McCarthy and even Trump "could" be subpoenaed by the committee as material witnesses. Kinzinger said that "for too long, we’ve been pretending that Jan. 6 didn’t happen."

He said he never expected to be in this position, "but when you have these conspiracies that continue to thrive, when you have lies and misinformation that continue to thrive, it’s essential for us as members of Congress to get to the answers."

Shortly after the insurrection, almost every Republican denounced the violent mob – and Trump himself, who told his supporters to "fight like hell" to overturn his defeat. But many have softened their tone in recent months and weeks. And some have gone farther, with Georgia Rep. Andrew Clyde saying a video of the rioters looked like "a normal tourist visit" and Arizona Rep. Paul Gosar repeatedly saying that a woman who was shot and killed by police as she was trying to break into the House chamber was "executed."

Others have falsely claimed that Democrats or liberal groups were responsible for the attack. On Tuesday, a group of GOP members plans to hold a news conference about the insurrectionists who were arrested, calling them "prisoners."

The officers testifying have become increasingly politically active in recent months and went from office to office in May to lobby Senate Republicans to support an outside commission to investigate the insurrection. The Senate GOP ultimately rejected that effort, even though that panel would have been evenly split between the parties.

In June, the group watched from the gallery as the House voted to form its own investigation instead. After that vote, members of the group said they were frustrated with the Republican response – only Cheney and Kinzinger had voted for the panel. Fanone, shaken, said, "it’s very personal for me." Dunn said he couldn’t believe that so many of them would vote against an investigation.

"I didn’t think it would be that close," Dunn said. "I thought it would be, everybody wants to get to the bottom of it."