A fiery Massachusetts U.S. Sen. Elizabeth Warren warned Friday that President Donald Trump and his Republican allies are preparing to deliver "a knockout blow" to the nation's middle-class.

The liberal icon delivered the comments to a packed theater in the heart of Manhattan's Times Square. It was the final scheduled stop in a book tour that featured a half-dozen appearances nationwide over the last two months.

She read from the book, "This Fight is Our Fight: The Battle to Save America's Middle Class," before exciting the overwhelmingly liberal crowd with aggressive rhetoric that demonstrated her appeal as a possible 2020 presidential contender.

"What Donald Trump and the Republican majority in the House and the Senate want to do to us, is they want to deliver the knockout blow to the middle class," Warren charged.

"Fighting back matters," she added. "Yeah, it's hard. If it were easy someone else would have already done it."

Like past appearances on the book tour, Friday's appearance felt as much like a political rally as an author reading, with Warren, the former Harvard Law School professor, pacing about the stage instead of standing behind the lectern.

Warren, 67, has downplayed any interest in the 2020 presidential contest, which she did not address Friday night, but it was on the minds of many in the audience.

Evan Davidoff, 31, of New York City, was wearing a green "Bernie 2020" T-shirt. Despite the shirt, he said his favorite early prospects are California Sen. Kamala Harris, Warren and New York Sen. Kirsten Gillibrand.

"I would love to see a woman president, but one that's strongly in the progressive camp," Davidoff said.

Sitting a few rows away, 36-year-old education worker Sarah Niglio said she liked Warren so much that she'd volunteer for her campaign, if she ran.

"I wanted her to run this past election," said Niglio, of Brooklyn.

Warren used heated rhetoric throughout her remarks, lashing out at Trump and his Republican colleagues in Washington for trying to "destroy our health care system" and letting everyone but the rich "eat dirt."

"The character of this nation is being tested," she said.

"The character of a nation is not the character of its president," she said. "The character of a nation is the character of its people."