Sen. Elizabeth Warren (D-Mass.) stumped for Democratic presidential nominee Hillary Clinton in Manchester, N.H., on Monday, where she mocked Donald Trump's calling Clinton a "nasty woman" during their last presidential debate. (Reuters)

Republican presidential nominee Donald Trump warned Monday that his candidacy represents “the kind of change that arrives only once in lifetime” and launched scattershot attacks against his Democratic opponent Hillary Clinton.

“She lies more than any human being,” Trump said of Clinton during a raucous rally in Tampa, his final stop during a day of campaigning in Florida, a must-win state for him.

Over the course of a half hour, Trump attacked Clinton for, among other things, using what he called an “illegal email server,” having “abused” the Hispanic and African American communities and advocating an increased U.S. role in ending the civil war in Syria.

“If you look at her plans for Syria, these are the plans of a child,” Trump said.

He implored his supporters to go the polls, suggesting no other candidate would be capable of ushering in the kind of change needed in Washington.

Speaking to a Fla. crowd Oct. 23, Republican presidential nominee Donald Trump said Democratic rival Hillary Clinton is "trigger-happy" and wants to start a war in Syria. (Reuters)

“In four years, it’s not going to happen,” Trump said. “You’ve got get out and vote. This is it.”

Trump also took aim at the Affordable Care Act on a day when government figures showed that premiums for plans sold through HealthCare.gov are increasing next year by an average of 25 percent.

“It’s over for Obamacare,” Trump said, declaring the program supported by Clinton “a disaster” and again pledging to repeal it.

With just 15 days until the election, Trump’s rally capped a long day of volleys between the two candidates.

Earlier Monday, Sen. Elizabeth Warren (D-Mass.), a top Clinton ally, launched a broadside against Trump, saying his disrespect for women would be his undoing in the election.

Appearing at a rally with Clinton outside Manchester, N.H., Warren said Trump “disrespects, aggressively disrespects, more than half the human beings in this country.”

Donald Trump vs. Hillary Clinton on the issues

“He thinks because he has a mouth full of Tic-Tacs that he can force himself on any woman within groping distance,” she said, referring to a 2005 video in which Trump spoke in lewd terms about women and then took the breath mints as he explained he liked to kiss women without asking their permission.

Riffing on Trump’s reference to Clinton as “a nasty woman” during their third presidential debate, Warren suggested to him that women would be the ones to dash his White House hopes.

“Well, I’ve got news for you, Donald Trump: Women have had it with guys like you. And nasty women have really had it with guys like you,” she said. “Yeah, get this Donald: Nasty women are tough, nasty women are smart, and nasty women vote.”

Trump also spent much of Monday arguing that the national media has deliberately skewed polls to undermine his candidacy and that he is winning.

Early in the day, during a discussion with farmers at Bedner’s Farm Fresh Market in Boynton Beach, Fla., Trump devoted nearly half of his seven-minute public remarks to criticizing the news media.

“I believe we’re actually winning,” he said, speaking in a thatched-roof structure adorned with decorative gourds. He asserted that the majority of public opinion polls, which show Clinton leading nationally and in most battleground states, reflect the “crooked system, the rigged system I’ve been talking about since I entered the race.”

During his evening rally in Tampa, Trump pointed toward the assembled press and said: “These people are among the most dishonest people in the world, the media. They’re trying to fix the election for Crooked Hillary.”

At stops in both St. Augustine and Tampa, Trump turned his fire on Clinton’s use of a personal email server while secretary of state. He said the FBI and Department of Justice had inappropriately let her off the hook.

“We have to investigate the investigation, folks,” Trump said.

He also seized on a Wall Street Journal story that reported that the political action committee of Virginia Gov. Terry McAuliffe (D), a leading Clinton supporter, gave $452,500 to a Northern Virginia state Senate candidate last year.

The candidate, Jill McCabe of Loudoun County, is married to FBI Deputy Director Andrew McCabe, who oversaw the bureau’s investigation into Clinton’s use of the private server. The state Democratic Party reportedly gave McCabe’s campaign another $207,788.

Trump called the donations “absolutely disgraceful” and alleged without presenting evidence that, “Hillary knew this money was being paid.”

Aides to McAuliffe and others said Monday that the timeline of events was inconsistent with any suggestion of wrongdoing.

McAuliffe’s support of Jill McCabe was part of a much broader effort at the time to try to win back a Democratic majority in the Virginia Senate, and his PAC gave greater amounts to other candidates. At the time McAuliffe recruited Jill McCabe to run for office, her husband was in another job, and there was no publicly known FBI investigation into the Clinton emails.

By the time Andrew McCabe was promoted to deputy director and assumed responsibility for the Clinton email investigation, his wife had been out of politics for several months.

Trump on Monday also addressed the latest accusations of inappropriate sexual contact made against him, saying of the accuser, an adult film performer, “Oh, I’m sure she’s never been grabbed before.”

Calling into WGIR radio’s “New Hampshire Today,” Trump characterized the allegations against him as “total fiction,” including the behavior alleged by Jessica Drake. On Saturday, she accused Trump of grabbing and kissing her without permission and offering her money to go up to his hotel room about a decade ago.

“She’s a porn star,” Trump said. “You know, this one that came out recently, ‘he grabbed me and he grabbed me on the arm.’ Oh, I’m sure she’s never been grabbed before.”

Clinton and her backers sought to capi­tal­ize on Trump’s declining poll numbers by lifting up candidates lower on the ballot this fall. The appearance with Warren was also designed to promote the candidacy of Democratic Gov. Maggie Hassan.

Warren’s appearance was part of the Clinton campaign’s effort to flood swing states with high-profile endorsers as the campaign comes to a close. It was also a tacit show of unity between Clinton and very liberal voters who consider Warren a champion and who, in New Hampshire, preferred liberal primary challenger Sen. Bernie Sanders over the moderate Clinton by a wide margin.

But mostly Warren, whose lines got louder applause than Clinton’s, was there as the best provocateur the Clinton campaign can field against Trump. He has engaged in several fierce attacks on Warren, often via Twitter.

“She gets under his thin skin like nobody else,” a delighted Clinton at the start of her remarks.

Later Monday, Clinton attended a high-dollar fundraising party in Manhattan with a birthday theme and entertainment by singer and composer Stevie Wonder. Clinton turns 69 on Wednesday. Aides said about 300 people attended, paying at least $10,000 apiece.

The New York event and another Tuesday in South Florida are likely to be Clinton’s last in-person fundraisers of the campaign. They cap a 19-month run since she announced for president in April 2015 in which the candidate rarely went more than a few days without headlining some kind of event with paying guests.

President Obama also plugged Clinton’s candidacy on Monday.

“The good news is that at the moment the polls show that Hillary is enjoying a lead,” Obama said outside a fundraiser in La Jolla, Calif. But he added that the “volatile” nature of race meant that “we can’t take anything for granted.”

“There are a lot of states like Ohio and Florida that are way too close to call,” he said, adding that it was important to “make sure that people actually turn out to vote.”

Trump started the week with a focus on two critical states in the Southeast: Florida and North Carolina. In a sign of the intense battle over Florida, Trump’s plane and that of the Democratic vice-presidential nominee, Sen. Tim Kaine of Virginia, were parked on the same Miami tarmac Monday.

Before leaving Miami, Trump did a radio interview with WBT Radio host Bo Thompson, making his case to listeners in Charlotte.

He accused the media of engaging in “a pile-on, the likes of which nobody’s ever seen.”

Despite his claims elsewhere that he’s winning, Trump conceded during the interview that he’s trailing in the polls.

“I think we’re gonna have — whether it’s Brexit or beyond Brexit, I think we’re gonna have a Brexit situation,” said, referring to the British referendum in which voters unexpectedly decided to leave the European Union. “You know, that one was behind in the polls, and I guess I’m somewhat behind in the polls but not by much. I mean, in your state, I’m 1 point, 2 points and even in three polls. 1 point, 2 points and even.”

Trump also announced Monday that his Facebook page would start hosting “nightly campaign coverage from Trump Tower.”

He did something similar before the final debate, promoting a webcast featuring surrogates and a video message from his daughter Ivanka. The announcement comes as some observers have speculated that Trump might start a media venture if he is not elected president. He has sought to tamp down such speculation.

Sullivan reported from Boynton Beach, Fla. Gearan reported from Manchester, N.H. Juliet Eilperin and Gregory S. Schneider in Washington contributed to this report.