Expelled by their Republican colleagues for an act of protest, Justin Jones and Justin J. Pearson were no longer members of the Tennessee House of Representatives on Friday. They could not advocate for their constituents in Nashville and Memphis, take to the floor again to push for gun control legislation or even access the building after hours.

But instead of sidelining the Democratic lawmakers, the expulsions have sparked outrage and galvanized national support within their party, and the two young Black lawmakers are poised to return to the state legislature — as soon as next week — with a platform and profile far surpassing what they had just days ago.

On Friday, Vice President Kamala Harris made a hastily arranged visit to Nashville to meet with the state lawmakers, and President Biden, who described the Republicans’ actions as “shocking” and “undemocratic,” called the ousted Democrats to offer his support and invite them to the White House.

“That made these individuals martyrs,” Representative Antonio Parkinson, a Democrat from Memphis, said of the expulsions. “It’s going to be extremely hard to silence them.”

Mr. Jones and Mr. Pearson were expelled on Thursday for interrupting debate last week by using a bullhorn to lead a gun control protest in the chamber in the wake of a deadly school shooting in Nashville. Republican leaders argued that the two lawmakers and Representative Gloria Johnson, who joined the protest but survived an expulsion vote, had brought “disorder and dishonor to the House of Representatives.”

Critics said that the expulsions were an overreaction that defied the will of the voters who had elected Mr. Jones and Mr. Pearson in Nashville and Memphis, the state’s two largest cities, which also have large Black and Democratic-leaning populations. Democratic lawmakers and activists also warned that the expulsions could have dangerous repercussions, including encouraging lawmakers in Tennessee and other states controlled by a single party to use the measure as a tool for silencing dissenting voices.

The outrage was also driven by race, as some lawmakers, activists and others said they believed that it was a factor in the final outcome of the votes: The two young Black lawmakers were ejected, but the third lawmaker involved, Ms. Johnson, a white Democrat from Knoxville, avoided the same fate by a single vote. “It might have to do with the color of my skin,” Ms. Johnson said on Thursday after seven Republicans joined Democrats in voting against her expulsion.

“Think about that,” Representative Parkinson said. “What signal does that send to the rest of the world? What does that say about who you are? It didn’t have to happen. That’s the worst part about it.”

Representative William Lamberth, the Republican majority leader, dismissed that assertion, arguing that Mr. Jones and Mr. Pearson had been “trying to incite a riot” and that Ms. Johnson had a clearer case for why she should be spared expulsion.

“They did not see Representative Johnson yelling, they did not see her with a sign, they did not see her with the bullhorn,” he said of his Republican colleagues. “They did see the other two members.”

Mr. Lamberth said that race was not a consideration. “All the resolutions were the same,” he said, “and the strength of the evidence against two of the representatives was stronger than the other.”

Representative Charlie Baum, who represents Murfreesboro, a rapidly growing city about 30 miles from Nashville, was the sole Republican to vote against the expulsion of all three Democrats.

Mr. Baum said that he would have preferred to work with the three lawmakers to improve House deliberations and that he had heard from his constituents, who overwhelmingly opposed expulsion. And during Holy Week, he added, he was “interested in showing some grace.”

The fate of the seats in the immediate term now rests with local officials in Nashville and Shelby County, where the lawmakers’ districts were. The Shelby County Commission will decide whether to appoint Mr. Pearson. Some of the 13 commissioners have indicated their support. Others said they were still considering their options as they were thrust into the middle of a contentious situation.

“I’m taking it all in,” Mick Wright, one of the commissioners, said in an email on Friday. “I believe both sides could do a better job listening to and respecting one another. That’s all I have to say for now.”

Representative Torrey Harris, a Memphis Democrat, said on Friday morning that he and other lawmakers planned to meet that evening with commissioners from Shelby County, which includes Memphis, about the process for returning Mr. Pearson to the Capitol.

“What’s best for Shelby County is for Representative Justin Pearson, who was elected by those people, to be sent back up here to continue to represent them throughout the rest of this session,” he said.

In Nashville, where many members of the Metropolitan Council have signaled their support for returning Mr. Jones to his seat, the expulsion has worsened an already inflamed relationship between state and city leaders. Nashville sued the state last month over a law that would slash by half the size of the council, which governs Nashville and Davidson County.

“I’m angry, sad and enraged,” Bob Mendes, an at-large member of the council, said of his reaction to watching the proceedings. “Surprised is not on the list because nothing the supermajority does really surprises me.”

The demonstration on the House floor reflected the grief and anger that have engulfed Nashville after an armed assailant stormed into the Covenant School, a small, private academy in the city, and killed three 9-year-old students and three adults. The fury over the shooting and a resistance by the legislature to pursue gun control measures drew hundreds of protesters to the Capitol.

On Thursday, enraged demonstrators filled the corridors of the state building, chanting their support for the three lawmakers. As infuriated as they have been by the process, activists said the moment was also inspiring others to become involved. “My phone has not stopped ringing,” said Tequila Johnson, the executive director of the Equity Alliance, a grass-roots social justice organization in Nashville.

The demonstrations over guns came as the Republican supermajority has pushed ahead with an aggressive conservative agenda, including adopting a law restricting drag performances and another measure blocking gender-affirming care for transgender minors. Last Friday, a federal judge temporarily blocked the implementation of the drag law, hours before it was set to go into effect.

Tennessee has also been buffeted by disaster: On Friday, President Biden approved a disaster declaration for a swath of the state shredded by tornadoes this month. And it has had to grapple in recent months with anger over police brutality after Tyre Nichols, a 29-year-old Black man, was fatally beaten by Memphis officers in January.

Mr. Pearson, 28, won a special election in a landslide to represent parts of Memphis, his hometown, just as Mr. Nichols’s death touched off renewed protests pushing for overhauling policing in the city and across the country. He decried the violence gripping Memphis. “We are dealing with an immense amount of grief from his murder by police and my own classmate’s murder by someone else in the same week,” he said in an interview with NPR in January.

He had gained prominence as a critic of a crude oil pipeline proposed to run through predominantly Black neighborhoods of South Memphis, a project that was canceled in 2021.

Supporters of Mr. Jones and Mr. Pearson invoked civil rights leaders of the past as they described them and their approach to politics. Mr. Jones often referred to “good trouble,” the term indelibly linked to John Lewis, the congressman and activist who died in 2020, as a mantra for employing activism to confront racism and discrimination.

Before winning an election to serve in the state legislature, Mr. Jones had staged a sit-in at the Capitol, demanding the removal of a bust of a Confederate general. In 2020, after the murder of George Floyd, Mr. Jones became known as a leader of the People’s Plaza Protest, a continuous two-month demonstration outside the Capitol.

“Justin Jones’s constituents knew who Justin Jones was and that’s who they elected,” said Elizabeth Waites, a resident of Mr. Jones’s former district, who voted for him twice.

Mr. Jones and Mr. Pearson had run into turbulence before the demonstration last week. When Mr. Pearson opted to wear a dashiki on the House floor, defying a custom of men wearing a suit and tie, he was chastised by Republican lawmakers. “If you don’t like rules, perhaps you should explore a different career opportunity that’s main purpose is not creating them,” Tennessee House Republicans said in a post on Twitter.

But after Republicans attacked the lawmakers for the demonstration on the House floor, Bryan Richey, a Republican lawmaker from the Knoxville suburbs, tried to discourage his colleagues from ejecting all three. He could envision how it would reverberate beyond Tennessee. (He voted against expelling Mr. Pearson and Ms. Johnson, but did support ejecting Mr. Jones.)

“If you expel them, they’re just going to get blown up to a level that none of y’all are ever going to see,” Mr. Richey said, recounting what he told other lawmakers considering expulsion. “And that’s exactly what’s unfolding right now.”

Reporting was contributed by Jamie McGee and Emily Cochrane.