Speaking at a campaign event in Portsmouth, New Hampshire, where she picked up the endorsement of Sen. Jeanne Shaheen, Clinton spoke about women's issues and used the occasion to take aim at Trump.

"Mr. Trump insults, he dismisses women ... he has been throwing a lot of heat my way," Clinton said. "That's fine; as Jeanne said, I can take it. But I do find a lot of what he says pretty ridiculous."

She also mocked his claims that he would be a champion for women's rights, including his oft-repeated vow that he "cherishes" women.

"If it's all the same to you, Mr. Trump, I would rather you stop cherishing women and start respecting women," Clinton said to loud applause.

Hours later, Trump, the GOP's clear leader in presidential polls, fired back on Twitter.

"Hillary Clinton made a speech today using the biggest teleprompter I have ever seen. In fact, it wasn't see through glass, it was black," he began.

Six minutes later, Trump continued:

"Hillary said such nasty things about me, read directly off her teleprompter...but there was no emotion, no truth. Just can't read speeches!"

He then knocked Clinton -- as well as Jeb Bush, another one of his favorite targets -- for accepting donations, which he believes makes them beholden to special interests and lobbyists.

"Remember that I am self-funding my campaign. Hillary, Jeb and the rest are spending special interest and lobbyist money.100% CONTROLLED"

Shaheen, one of Clinton's most high-profile and public endorsements to date, was effusive in her support of Clinton.

"She will proudly stand with women, she will proudly stand with Latino Americans, she will proudly stand with the LGBT community, she will proudly stand with teachers, and she will proudly stand with the hard working men and women of labor," said Shaheen, the only woman to have been elected to both a state governorship and the U.S. Senate.

"No one else running for president has the depth of knowledge and experience that she has. I trust Hillary to fight for the middle class, because it's what she's always done," she added.

Shaheen later tweeted her support of Clinton.

Speaking on the 20th anniversary of her address in Beijing, where then-first lady Clinton made an impassioned plea for greater equality for women in China and around the world, the current Democratic front-runner vowed to fight for women's issues, including child care, paid family leave and abortion rights.

"What is good for women is good for America," Clinton said. "These are all women's issues, but they are also American issues. ... If we women stand together and fight tougher, we can make our country stronger, we can make our country fairer, we can give our children and grandchildren the brighter future they deserve."

Clinton's remarks came during a day-long swing through New Hampshire, a state that she won in 2008 but polls show is recently starting to favor her challenger, Vermont Sen. Bernie Sanders.

Some of the people at Clinton's event were even Sanders supporters, drawn by their interest in the former secretary of state's campaign.

Jack Chambers, a New Hampshire Democrat, said he thinks Sanders will win the New Hampshire primary come 2016, but won't win the Democratic nomination.

"Sanders is like a dog that is chasing a car," Chambers said. "The car stops and he has caught the car, so he is thinking, 'Now what do I do?'"

Clinton also visited a local Portsmouth bookstore, RiverRun Bookstore, where she was greeted by large numbers of well-wishers and supporters.

"Hillary," said one woman as they shook hands on the street, "stay strong and don't let them get you down."

Clinton was met on the streets of Portsmouth by several people who supported her failed 2008 campaign.

After one woman introduced herself as a 2008 supporter, Clinton said confidently, "Well, we are going to do it this time."

Clinton capped her day off with a stop at an event for organized labor supporters in Manchester. After meeting with labor leaders, Clinton gave a speech that focused squarely on protecting workers rights to bargain.

As president, Clinton said, she "will go to that bully pulpit and I will make the case, day in and day out, that we need to reverse the erosion of unions in America."

"We have watched a steady assault on the rights to organize and bargain collectively," she told the supportive audience, adding, "if you don't have a strong labor movement, you aren't going to have a strong middle class."

CNN's Eugene Scott reported from Washington. CNN's Dan Merica reported from New Hampshire.