Democratic presidential candidate Bernie Sanders challenged frontrunner Hillary Clinton on her paid speeches to Wall Street on the eve of a crucial voting day, with five more states headed to the polls on March 15. (Reuters)

Presidential hopefuls in both parties made frenetic pitches across the Midwest and Southeast on Monday on the eve of presidential primaries in five states that could shore up the two front-runners — or breathe new life into the lagging campaigns of their challengers.

On the Democratic side, Sen. Bernie Sanders staged rallies in four of those states, trying to pull off more come-from-behind wins in states damaged by trade and claim momentum from Hillary Clinton, who enjoys a sizable lead but has not been able to seal the nomination.

For the Republicans, Tuesday offers a chance for Donald Trump’s remaining rivals to slow his march to the nomination with two winner-take-all contests that have particularly high stakes for a pair of favorite sons, Sen. Marco Rubio of Florida and Gov. John Kasich of Ohio.

Multiple polls in the days leading up to Tuesday’s contests showed Sanders closing in on Clinton in three states in the industrial Midwest — Missouri, Illinois and Ohio. But polls show Clinton far ahead in Florida and in North Carolina, setting up the possibility of an outcome parallel to last week’s contests, when Sanders scored a narrow and surprising victory in Michigan, yet Clinton came away with a widened lead in the delegate count because of her resounding victory in Mississippi.

Hillary Clinton, accompanied by the Rev. Jesse Jackson and mothers who have lost children to gun violence, visits the Kids Off the Block memorial in the Roseland neighborhood of Chicago on Monday. (Melina Mara/The Washington Post)

In other words, Clinton appears poised to continue her progress toward the Democratic nomination, but ever more bloodied by her battles with Sanders.

On the campaign trail Monday, the senator from Vermont continued to hammer Clinton, as he did in Michigan, on the issue of trade — arguing that he has been a far stronger ally in the fight to protect manufacturing jobs.

“You in Ohio and in the Midwest know about the disastrous trade policies,” he told an audience packed into a theater in Akron, where a once-thriving tire industry has experienced a major decline.

“It took me about 13 seconds to figure out that NAFTA was written by corporate America, that its goal was to shut down factories and plants in America, to move abroad to find cheap labor, and bring those products back into America. It didn’t take a PhD to figure that out,” Sanders said.

Clinton, meanwhile, appeared to take sharper aim at Trump, the Republican front-runner, than at Sanders. At an MSNBC town hall in Springfield, Ill., Clinton said Trump is evoking the kind of mob violence “that led to lynching.”

“When you are inciting mob violence, which is what Trump is doing in those clips, there’s a lot of memories that people have,” she told Chris Matthews. “People remember mob violence that led to lynching. People remember mob violence that led to people being shot, being grabbed, being mistreated.”

Clinton also made campaign stops Monday in Chicago and Charlotte.

The Ohio GOP primary could be the Republican establishment's last chance to stop Donald Trump. (Peter Stevenson/The Washington Post)

Kasich, who has said he will drop out of the Republican contest if he doesn’t win Tuesday’s primary in his home state of Ohio, made two appearances there Monday with Mitt Romney, the 2012 Republican nominee. It was the first time Romney had stepped out on the trail since his recent broadside against Trump.

Romney, who has pledged to support any GOP candidate who can defeat Trump, stopped short of endorsing Kasich — but had plenty of nice things to say about him during an event at an airplane museum in North Canton, Ohio, where the backdrop included a fighter jet, a helicopter and a ­“Patton”-size American flag.

“You’re the ones who are going to decide if he becomes the next president of the United States,” Romney said. “You look at this guy, and unlike the other people running, he has a real track record. He has the kind of record that you want in Washington. That’s why I’m convinced that you’re going to do the right thing tomorrow.”

Tuesday could also be the last stand for Rubio, a candidate once touted as “the Republican savior” who more recently has badly trailed Trump in polls in his home state of Florida.

Barnstorming there Monday, Rubio said the mogul’s abrasive rhetoric has already earned him a spot in history — for all the wrong reasons.

“I don’t think there’s anyone in the history of American politics that compares to the vulgarity of a Donald Trump candidacy,” Rubio told reporters. He repeated himself to emphasize his point: “In the history of American politics.”

Before that, the senator from Florida campaigned outside a restaurant where supporters held up signs and chanted his name. Sleeves rolled up under the bright sunshine, Rubio encouraged his backers to keep fighting for him, and he framed Tuesday’s primary as a chance to go in one of two very different directions.

“Tomorrow is a choice between optimism and fear,” Rubio told the crowd.

Trump struck a dismissive tone Monday amid harsh scrutiny of the sometimes-violent clashes at his rallies, insisting during an event in Hickory, N.C., that violence has not been an issue.

“The press is now going, they’re saying, ‘Oh, but there’s such violence.’ No violence. You know how many people have been hurt at our rallies? I think, like, basically none, except maybe somebody got hit once,” Trump said at Lenoir-Rhyne University after several protesters were escorted out during the first of three interruptions.

“It’s a love fest. These are love fests,” Trump added later. “And every once in a while . . . somebody will stand up and they’ll say something. . . . It’s a little disruption, but there’s no violence. There’s none whatsoever.”

Trump was interrupted just three times Monday by protesters, who had a significantly smaller presence than at events in recent days.

The candidate said he has been treated with a double standard by media outlets, which he says report protesters at his events but do not cover protests at other candidates’ rallies. But the scale and frequency of the protests at Trump’s events undeniably outstrip those at his rivals’ events, culminating in the violent clashes in Chicago last week.

Former Alaska governor Sarah Palin has been campaigning for Trump in Florida but said she planned to leave early because her husband was seriously injured in “a little wreck on a snow machine.”

Palin said that even though she was dealing with this family crisis, it was important to spend time helping Trump get elected.

“What we don’t have time for is all that petty, punk-ass little thuggery stuff that’s been going on,” she said, referring to the protesters who have targeted Trump’s rallies in Chicago and elsewhere. She accused the protesters of endangering the First Amendment rights of Trump’s supporters to peacefully assemble, and charged the media with “being on the thugs’ side.”

In Rockford, Ill., Cruz made news by laying out the one scenario in which he would not support Trump as the nominee: “If, for example, he were to go out on Fifth Avenue and shoot somebody, I would not be willing to support Donald Trump.”

Cruz is looking for strong performances in Illinois, Missouri and North Carolina to cut any delegate lead Trump might build Tuesday. Missouri and Illinois, where Cruz was scheduled to make five stops Monday, border parts of Iowa, which gave him his first victory.

Back on the Democratic side, there have been several signs that the unexpectedly competitive contest with Sanders has taken a toll on Clinton. She regularly logs 18-hour days on the trail, mixing retail campaigning — downing a Guinness beer in an Irish bar ahead of St. Patrick’s Day, for example — with rallies and a seemingly never-ending stream of town hall meetings and debates.

That pace may help explain a series of gaffes that have put Clinton in hot water with her supporters and created problems that could haunt her in the general election if she wins the nomination.

Friday morning, the day of Nancy Reagan’s funeral, Clinton mistakenly praised the former first lady for “starting a conversation” about HIV/AIDS. Clinton quickly apologized, but the backlash from the LGBT community was intense, despite efforts by the campaign to reassure them that she had made an honest error.

The next day in St. Louis, Clinton suggested that Sanders had been absent during her 1993 push for health-care reform. On Twitter, a Sanders aide quickly blasted out an archival video showing the senator standing right behind Clinton during a news conference about the effort.

Twenty-four hours after that, Clinton answered a question about coal country with a cringe-worthy response: “We’re going to put a lot of coal miners and coal companies out of business, right?”

On Monday, Clinton spokesman Brian Fallon tried to clean up after Clinton, saying Republicans were trying to twist her words to suggest she showed a disregard for coal workers.

“Obviously she was making the exact opposite point: that we have to take proactive steps to make sure coal workers, their families and their communities get not just the benefits they’ve earned but also the future they deserve,” he said. “Any suggestions otherwise are false.”

Sanders also made campaign stops Monday in North Carolina and Missouri, and he was scheduled to end the day with a late-night rally in Chicago.

The only place with a primary he intended to skip was Florida, where polls have shown Clinton with a sizable lead in Tuesday’s most delegate-rich contest.

Florida’s primary is closed, meaning independents, who have sided with Sanders in large numbers in other states, won’t be able to participate. The state is also home to large numbers of seniors, who have gravitated far more heavily toward Clinton elsewhere.

Juliet Eilperin in Washington; Jenna Johnson in Tampa; Abby Phillip in Springfield, Ill.; Sean Sullivan in Melbourne, Fla.; David Weigel in North Canton, Ohio; and Katie Zezima in Peoria, Ill., contributed to this report.