It is a glimpse at an alternate political universe: the speech Hillary Clinton would have given on election night, had she not lost to Donald J. Trump in 2016.

Mrs. Clinton reads the discarded speech aloud for her offering on the streaming site MasterClass, which features lessons from prominent figures in the arts, business, food and other fields.

Mrs. Clinton is promoting her class, “The Power of Resilience,” on Twitter, and a clip of her reading an excerpt from the speech — and tearing up at one point — was released by the “Today” show on Wednesday.

The video — and the class — generated mockery from Mrs. Clinton’s detractors on the right and the left, as well as praise from her supporters, who said they found it moving.

“In this lesson, I’m going to face one of my most public defeats head-on by sharing with you the speech I had hoped to deliver if I had won the 2016 election,” Mrs. Clinton says in the video.

“I’ve never shared this with anybody,” she says. “I’ve never read it out loud.”

In the long-shelved victory speech to “my fellow Americans,” Mrs. Clinton strikes themes of unity, and reflects on what would have been her history-making election as the first female president.

She recalls meeting women who were born before women had the right to vote as well as boys and girls who didn’t understand why a woman had never been president before.

“Now they know, and the world knows, that in America, every boy and every girl can grow up to be whatever they dream — even president of the United States,” Mrs. Clinton says.

She chokes up when she discusses her mother and mentor, Dorothy Rodham, who grew up in poverty and was abandoned by her parents as an 8-year-old girl. She died in 2011 at age 92.

“I dream of going up to her, and sitting down next to her, taking her in my arms, and saying, ‘Look at me. Listen to me. You will survive,’” Mrs. Clinton says. “‘You will have a good family of your own and three children. And as hard as it might be to imagine, your daughter will grow up and become the president of the United States.’”

Kathleen Hall Jamieson, a professor of communication at the University of Pennsylvania’s Annenberg School for Communication, said she found that part of the speech striking.

“Had Hillary Clinton communicated more of that narrative, she would have had more of a successful presidential run,” Professor Jamieson said. “I read that as an interesting, coherent explanation of what would have motivated Hillary Clinton to be a public servant.”

Mrs. Clinton had planned to deliver the speech at an elaborate celebration on the night of Nov. 8, 2016, complete with confetti shaped like glass shards that would fall from the glass ceiling of the Jacob K. Javits Convention Center in Manhattan.

Instead, she gave a hastily scheduled speech in a dreary hotel ballroom on the day after the election, in which she said the country was “more deeply divided than we thought.”

“This loss hurts,” she said that day. “But please never stop believing that fighting for what’s right is worth it.”

For scholars of the American presidency, the speeches candidates prepare and then discard on election night can be fascinating, Professor Jamieson said, adding that she would have loved to have read the victory speeches prepared by Barry Goldwater, Hubert H. Humphrey and George McGovern, among other losing candidates.

“There’s always a curiosity about where we were about to go, or what we were about to experience,” she said. The speeches, she said, hint at “the course not taken.”

Tim Hogan, a former spokesman for Mrs. Clinton’s 2016 presidential campaign, said on Twitter that watching her read the speech and choke up “has me sobbing right now.”

Others were not as moved.

“I’m not sure 1) Why Hillary Clinton is teaching a ‘MasterClass’ on anything or 2) Why MasterClass is selling access to watch her cry while reading her 2016 victory speech that was all for naught,” Spencer Brown, a managing editor of the conservative website townhall.com, wrote on Twitter.

Jim Hobart, a Republican pollster and a partner at Public Opinion Strategies, said that reading the speech was simply a way to promote the class.

“She has a product to sell, a new product, and it’s clear that she thinks reading what would have been her 2016 acceptance speech is the best way to sell that product,” Mr. Hobart said. “I don’t think it’s really anything more than that.”

MasterClass charges $15 to $23 a month for subscriptions. The site plans to release a class from former President Bill Clinton on Dec. 19 and from former President George W. Bush in the spring.

Isabella Grullón Paz contributed reporting.