"As long as you are fighting for working families in America, I will be in the trenches fighting alongside of you," she said to more than 5,000 supporters at New York's Javits Convention Center. "Labor will always have a seat at the table when I am in the White House."
Clinton, a former New York senator, called her strong performance Tuesday "one for the history books," but she stopped short of claiming she had the nomination in hand even as she looked ahead to a battle with the eventual Republican nominee.
"The other side has a very different vision about what our country should look like, and how we should treat each other," she said, reprising her recent line that the country needed more "love and kindness" at a time when Republicans were more interested in "tearing people down."
Just blocks from apartment complexes and a corporate tower that bear
"Boy does it matter, when you are president, what you say, and how the rest of the world hears you," she said.
The procession of New York elected officials and labor leaders who preceded Clinton on stage were more blunt, warning of the threat Trump would pose if elected president.
New York Gov. Andrew Cuomo mocked the billionaire, impersonating his eccentric speaking style and obsession with building a wall along the border with Mexico.
New York Mayor
"It's amazing that some of the pundits think the people of this country won't be able to figure out that comparison. Because they will," he said. "The people are going to look at a billionaire who hasn't done anything for us versus someone who has been a champion of children and families, working people, for years."
Clinton vowed to run "a campaign that is about the future."
"If we do what we must in this election to bring out a positive message of what we can do together, who we stand for and what we stand for, we will go into the November election with the wind at our back," she said. "And if I'm so fortunate to be your president, we will work together to make it true."
New York doesn't hold its primary until April, by which time Clinton may well be the presumptive Democratic nominee. But she nonetheless asked for support.
"We need a big primary victory," she said. "With your help I know we can win the nomination, I know we can win in November, and I know we can build an America where we don't leave anyone out or anyone behind."