By MICHAEL BARBARO
The victories were lopsided. The celebrations were effusive. The delegates were piling up by the hundreds.
Both major parties must now confront the depth of skepticism, resistance and distaste for their front-runners, a sentiment that would profoundly shape a potential general election showdown between Mr. Trump and Mrs. Clinton.
Even as they watched the two candidates amass large margins on Tuesday, historians and strategists struggled to recall a time when more than half the country has held such stubbornly low opinions of the leading figures in the Democratic and Republican Parties.
“There is no analogous election in the modern era where the two top candidates for the nomination are as divisive and weak,” said Steve Schmidt, a top campaign adviser to George W. Bush in 2004 and John McCain in 2008. “There is no precedent for it.”
Mrs. Clinton’s commanding wins in the swing states of Ohio, North Carolina and Florida seemed to hobble the once robust challenge of Senator Bernie Sanders. And Mr. Trump’s dominance in Florida, North Carolina and Illinois knocked out Senator Marco Rubio and propelled Mr. Trump even closer to the Republican nomination.
This would be the moment, under normal circumstances, when the de facto nominees, emerging victorious from the intramural skirmishes of their parties’ nominating contests, would invite an eager national electorate to take their measure. And in their victory speeches, both tried their best, issuing broad appeals for Americans to unite behind them.
But Mr. Trump has unnerved many Americans with his inflammatory oratory and radical-sounding proposals. And Mrs. Clinton, while viewed as a more seasoned and serious political figure, has struggled in her campaign to win the trust of the American electorate. And it is all but impossible for the country to take a fresh look at them.
America has lived with Mr. Trump and Mrs. Clinton, in a remarkably intimate fashion, for decades, processing their controversies, achievements and setbacks, from impeachment to marital breakdowns, Senate victories to flashy skyscraper openings. Voters’ impressions of them, with few exceptions, are largely formed and fixed. According to Gallup, 53 percent of Americans have an unfavorable opinion of Mrs. Clinton and 63 percent have such a view of Mr. Trump.
“You are talking about two universally known figures here,” said David Axelrod, the former Democratic strategist and former adviser in the Obama White House. “The strong feeling that each generates is unusual.”
The negative perceptions will be difficult to overcome.
Fewer than half of Republican voters across five states on Tuesday said Mr. Trump was honest and trustworthy. Even in the states where he won, a majority of voters do not view him as truthful.
And while majorities of Democratic voters viewed Mrs. Clinton as honest and trustworthy, she finished second to Mr. Sanders among those who said honesty mattered most in their decision.
That reality is forcing the Trump and Clinton campaigns to prepare for all-out warfare against each other, an improbably brutal dynamic for a pair of New Yorkers whose paths have crossed, repeatedly, for years — even on the way down the wedding aisle. (Mrs. Clinton and her husband, former President Bill Clinton, attended Mr. Trump’s third wedding, in 2005.)
They are devising appeals that are as much arguments that their all-but-certain opponent would be disastrous for the nation as they are messages trumpeting their own virtues or character.
Aides to both predict that a Clinton-Trump contest would be an ugly and unrelenting slugfest, as she pounces on his business practices and personal integrity, portraying him as unscrupulous robber baron, and he lacerates her over ethical lapses and sudden riches, painting her as a conniving abuser of power certain to be indicted in a federal investigation.
There is, both sides concede, plenty of material to mine, stretching back to 1980s Arkansas (for her) and 1970s New York (for him).
Voters are strikingly familiar with the candidates’ biographical vulnerabilities and political liabilities, interviews show, and they express disapproval in vivid, sweeping terms.
Kent Moore, 51, a Democrat from Charlotte, N.C., does not simply dislike Mrs. Clinton. He doubts her basic values.“She has no moral center,” Mr. Moore said.
He ticks off past sins: She favored free trade agreements that have killed American jobs, he said, and she supported the misbegotten 2003 war in Iraq. How, he wondered, could she beat Mr. Trump with a record like that?
Even those who vote for Mrs. Clinton harbor reservations. Renee White, 31, a Democrat in Youngstown, Ohio, is not entirely convinced that Mrs. Clinton, her choice in Tuesday’s primary, cares about people like her, she said. “A lot of people,” she said, “just don’t trust her at all.”
The views of Mr. Trump from Republicans are almost equally uncharitable and unwavering.
“Too crude and rude,” is how Nikki Heath, 59, a graphic artist from the Columbus, Ohio, area put it. She supports the state’s low-key, genial governor, John Kasich. She has written off Mr. Trump and his antics as “an embarrassment.”
The distaste is so strong that voters speak of a radical transformation (or personality transplant) required for them to consider backing Mr. Trump.
“He’s going to have to be completely different,” said Steve Rogers, an engineer in Ohio who will try to hold his nose and back him if he becomes the nominee.
Those dim assessments are not isolated, which is why the commanding tallies that Mr. Trump and Mrs. Clinton have collected are pushing both parties into uncharted waters. Should they clinch the nomination, it would represent the first time in at least a quarter-century that majorities of Americans held negative views of both the Democratic and Republican candidates at the same time.
The highest unfavorability rating for any nominee or front-runner was 57 percent, for the elder George Bush, in October 1992, as he emerged from a difficult first term in the White House. But his Democratic rival, Mr. Clinton, was widely liked: Just 38 percent viewed him unfavorably, according to Gallup.
The unpopularity of Mr. Trump and Mrs. Clinton is prompting Republicans and Democrats to weigh unusual considerations at the ballot box.
Lowell P. Weicker Jr., who sought the Republican nomination for president in 1980 and served as an independent governor of Connecticut in the 1990s, said he held Mrs. Clinton in low regard. But he holds Mr. Trump in even greater contempt. “I don’t like her,” Mr. Weicker said, “but I am sure going to vote for her over Trump.”