(Whitney Shefte/The Washington Post)

The overflow crowd at Busboys and Poets was black and white and shades in between, yuppies in chinos and activists in message T-shirts, bubbling with excitement to hear from the special guest at the restaurant’s open mic night.

Instead of a poet or a musician, Rep. Maxine Waters (D-Calif.) stepped onto the stage, showered with applause and cheers. Not many members of Congress could draw this kind of crowd — diverse and yet united behind a single goal. After taking a moment to thank the crowd for its greeting, Waters got right to the point.

“Donald Trump is someone that found his way to the presidency of the United States of America — I still don’t know how,” she said, drawing boos at the mention of the president’s name. “But he’s someone that I’m committed to getting impeached!”

The crowd exploded.

“He’s a liar! He’s a cheat! He’s a con man!” she said, each declaration punctuated by cheers. “We’ve got to stop his ass!”

(Victoria Walker/The Washington Post)

Waters has become the voice of a new generation of restless citizens. At age 78, the congresswoman’s political career is older than many of her new admirers. Her decades of forceful confrontation of institutional discrimination, inside and outside the political arena, has attracted fans far beyond the boundaries of her Los Angeles congressional district.

But much of her newfound celebrity can be credited to one word: impeachment.

Waters’s crusade against Trump — she did not attend his swearing-in and skipped his joint address to Congress two months ago — is popular with the young activists and progressives who have taken to the streets since his inauguration.

John Becker, a 32-year-old LGBT activist who was at the Busboys event, said Waters “recognizes, almost as no one else does, the peril that our country is in, and she is willing to say exactly what needs to be said. She is putting country first, and I wish that more of our representatives and elected officials would follow her example.”

Symone Sanders, who served as national spokeswoman for the unsuccessful campaign for the Democratic presidential nomination of Sen. Bernie Sanders (I-Vt.), said Waters reflected the outrage of progressives when she rejected the notion of trying to work with Trump, as some Democratic members of Congress suggested after the election. Even Senator Sanders was quoted as saying he would be willing to work with the president on trade reform and rebuilding the country’s infrastructure.

“That is not what the base wanted to hear, and that is definitely not what millennials wanted to hear,” Symone Sanders said of Democrats’ response to Trump. Just 37 percent of voters ages 29 or younger voted for Trump, according to exit polls.

It is clear that Waters is enjoying the attention. She is in demand on cable news and at progressive events such as January’s Women’s March on Washington. She is busy on Twitter (she jokes that she had to consult with her grandchildren to find out what it meant to “go viral”).

But for all of her followers on social media and in the streets, Waters is waging the campaign to impeach Trump largely on her own. Her concern centers on the question of whether Trump and his campaign knowingly worked with the Russian government to influence the outcome of the election, in which the businessman defeated Democratic nominee Hillary Clinton. Most of her Democratic colleagues are circumspect on the matter, calling for a vigorous, independent investigations, but rarely using the i-word.

Asked to respond to Waters’s call for impeachment in February, House Minority Leader Nancy Pelosi (D-Calif.) said Trump “has acted in a way that is strategically incoherent, that is incompetent and that is reckless. And that is not grounds for impeachment.”

“I’ve been criticized because people said, ‘Oh, you shouldn’t use the impeachment word.’ But I have a deep and strong feeling about what I’m hearing and what I’m seeing and what I’m learning,” Waters said in an interview with The Washington Post. That day, The Post reported a secret meeting between a major Trump supporter and a Russian with close ties to President Vladimir Putin, and BuzzFeed reported that former Trump adviser Carter Page had communicated in the past with a Russian intelligence agent.

“This involvement with so many of the people in his Cabinet with the Kremlin, with Putin . . . worries me and it bothers me,” she said.

Sarah Huckabee Sanders, the White House principal deputy press secretary, said of Waters: “Her calls for impeachment are baseless and ridiculous.”

Waters has nothing to lose. Her congressional seat is safe — she has received no less than 70 percent of the vote since her first congressional campaign in 1990. And among Democrats, the idea of impeaching Trump is appealing. Although only 30 percent of adults in a February Public Religion Research Institute poll said Trump should be impeached, 58 percent of Democrats supported the idea.

Still, neither Waters nor any of her Democratic House colleagues has put forth a resolution to begin the impeachment process. She acknowledges that there is not enough solid evidence that Trump colluded with the Russians.

“The investigations are very important. I think all of the signs are there, and when they connect the dots, when they have all the facts, you will see a change in the Congress,” said Waters, who is the ranking Democrat of the House Financial Services Committee. “Not only will Democrats be anxious to impeach, but Republicans as well.”

Removing a president from office is difficult, both practically and politically, says Michael J. Gerhardt, a constitutional law professor at the University of North Carolina’s School of Law. The Constitution sets a high bar: The House can call for an investigation if a president is suspected of “treason, bribery or other high crimes and misdemeanors.” The House Judiciary Committee decides whether there is sufficient evidence; if so, it draws up articles of impeachment. If the full House passes them, the Senate considers the charges and decides whether to convict the accused.

The House has voted to impeach only two presidents in the country’s history — Andrew Johnson in 1868 and Bill Clinton in 1998. The Senate acquitted both men. The House Judiciary Committee had begun preparing articles of impeachment against President Richard M. Nixon in 1974 for his role in the Watergate scandal, but he resigned.

With a particularly partisan environment in Congress, lawmakers will weigh the political risks of pursuing impeachment, Gerhardt said.

“When you have party unity like you do in current Republican Party, that makes it an additional hurdle to get over. The minority party in the House has virtually no power,” said Gerhardt, who testified during Clinton’s impeachment proceedings.

Waters’s record on progressive and civil rights issues is lengthy: Before joining Congress in 1991, she was a member of the California State Assembly, where she authored legislation forcing the state to divest its pension funds from companies doing business in South Africa at the height of the fight against that country’s apartheid system.

In 1992, she was introduced to a national audience during the Los Angeles riots following the acquittal of police officers charged in the beating of motorist Rodney King. Waters called for context, saying the violent reaction was a result of an ongoing sense of injustice in the city’s black communities. Two years later, she voted against President Clinton’s crime bill, which has been criticized for helping to fuel an explosion in the prison population that has disproportionately affected African Americans and Latinos.

In the House, she continued to articulate the concerns of poor people, women and people of color, and she chaired the Congressional Black Caucus in the late 1990s.

Nichole Christian heard Waters speak at an event in Detroit last month — “every fifth word was ‘impeachment’ ” — and came away invigorated.

Christian called the actions of Trump’s presidency “a daily slap in the face” to immigrants, women and African Americans. Waters, she said, was “somebody who has taken a principled stand. . . . She’s a politician doing an apolitical thing: speaking truth to power.”

As much as Waters is celebrated by progressives, she is castigated by conservative commentators and activists who point to an ethics investigation of her to undermine her arguments against Trump. Several years ago, Waters was investigated for — and cleared of — violating House conflict-of-interest rules after she sought federal aid for a bank in which her husband owned hundreds of thousands of dollars in stock.

Her moments of hyperbole and slip-ups also have become targets for conservative critics. While laying out her concerns about the Trump administration at a news conference in February, she said Putin had invaded Korea instead of Crimea.

And last month, Fox News host Bill O’Reilly, reacting to a Waters speech that was critical of Trump, disparaged her appearance, likening her hair to a “James Brown wig.” A backlash followed, and he quickly apologized.

But the eccentricities that have become targets for Waters’s critics have been glorified by her fans, who affectionately call her “Auntie Maxine.”

R. Eric Thomas of Elle.com helped fuel Waters’s popularity with a column in January on how Waters doesn’t just go in on Trump, she does so with style, employing dramatic eye rolls during interviews and a taunting moniker for Trump and his advisers who have ties to Russia — “the Kremin Klan.”

Thomas likened her to that certain aunt in the family who will set you straight when you are out of line. As he put it: “Honey, Maxine Waters is not the one. . . . She would like to cordially invite you to not come for her unless she sends for you.”

Like the time Waters dissed FBI Director James B. Comey. She emerged from a closed-door intelligence briefing with the air of someone who was not pleased to have wasted her time. When a reporter asked about the meeting she said simply: “The FBI director has no credibility!” And then walked away.

“Auntie! Auntie! Auntie!” the crowd at Busboys chanted as Waters wrapped up her talk.

“I did not know that an auntie could be loved by so many people!” she said. “I’m having the time of my life.”

Scott Clement contributed to this report.