As foreign capitals looked on in grim suspense, and with Tuesday's poll hanging in the balance, the 69-year-old Democrat gathered a galaxy of political and show business star power in Philadelphia, birthplace of the republic, to urge unity.
"Tomorrow, we face the test of our time," Hillary Clinton declared in front of 40,000 people, a record for her in a campaign where she has maintained a narrow opinion poll lead but has had less success than her Republican opponent in turning out passionate crowds.
"There is a clear choice in this election. A choice between division or unity, an economy that works for everyone, or only for those at the top; between strong, steady leadership, or a loose cannon who could put everything at risk."
At the same time Trump, the 70-year-old tycoon who turned his conservative party into a vehicle for populist bombast, concluded a last-gasp tour of swing states by painting his rival as doomed to defeat and the corrupt creature of a discredited elite.
"Do you want America to be ruled by the corrupt political class, or do you want America to be ruled, again, by the people?" he demanded, at a rally in New Hampshire, a state won in 2012 by President Barack Obama that Trump hopes to flip into his column.
Promising to end "years of betrayal", tear up free trade deals, seal the border, halt the drug trade and exclude all Syrian refugees, Trump told his supporters: "I am with you and I will fight for you and we will win."
Some 40 million Americans have already cast ballots in states that allow early voting, and tens of millions more will turn out on Tuesday to end what has become a long, gruelling and divisive campaign that has stirred dark undercurrents in the electorate.
Clinton remains favorite to succeed Obama and become the United States' first female leader.
But her campaign she has been dogged by allegations that she put US secrets at risk by using a secret private email server while at the State Department and the race remains perilously close in a handful of key states.
Support for Trump dropped fell when footage emerged last month showing him bragging about having sexually assaulted women, but polls have tightened as the big day approaches.
In a red pantsuit and full of smiles, Hillary Clinton blitzed three states and four cities in a marathon final day of campaigning Monday - with the help of two presidents, one rock Boss and Lady Gaga.
Clinton is used to epic travel days - as secretary of state, she logged nearly a million miles on the road.
On Monday, she left her home in Chappaqua, in the New York suburbs, to take on an itinerary of 3,200 kilometers.
Destinations: Pittsburgh, Pennsylvania; Allendale, Michigan; Philadelphia, Pennsylvania and Raleigh, North Carolina - three swing states, all vital to secure a historic win Tuesday and become America's first woman president.
The Democrat is looking to lock in key battleground states to block any path her Republican opponent Donald Trump might have to the White House.
About 2,500 people flocked to the campus of the University of Pittsburgh for Clinton's first rally - an outdoor event on a sunny autumn day.
"Tomorrow is the election, but that is just the beginning. We have to heal this country, we have to bring people together, listen and respect each other," she said in her classic stump speech, which lasted about 20 minutes.
Clinton briefly deviated from protocol by going to shake hands with some of those gathered in the streets outside the venue.
And that was that - her long motorcade of Secret Service agents, aides, and journalists headed back to the airport. Next stop: Michigan.
If Clinton is worried, it didn't show. Her staff added a few rallies to her final days on the trail - but not as many as Trump tacked on.
She headed to Grand Valley State University in Allendale, outside Grand Rapids, where Trump was to close out his campaign with a late night rally. The sun was still shining. More than 4,500 people turned out.
The Democrat's path to victory goes through the American Rust Belt - states like Pennsylvania, Ohio and Michigan, which voted for Barack Obama but are not as enthusiastic about Clinton.
"I want each and every one of you to be thinking through about all the issues you care about, because although my name and my opponent's name will be on the ballot, those issues and those values are on the ballot as well," she said.
After Michigan, it was back to Pennsylvania for a blowout rally in Philadelphia heavy with symbolism: tens of thousands gathered in front of Independence Hall, where both the Declaration of Independence and the Constitution were adopted.
"Tomorrow, we face the test of our time," Clinton said. "None of us wants to wake up and think that we could have done more."
She was joined by two presidents - her husband Bill and Barack Obama - and one of her most powerful surrogates, First Lady Michelle Obama.
"Philadelphia, you have somebody outstanding to vote for in Hillary Clinton," Obama said, passing the political mantle to his onetime top diplomat.
It was her biggest crowd of the campaign - officials put the size of the crowd at roughly 40,000 - 33,000 on Independence Mall, and thousands more beyond the security perimeter.
Rockers Bruce Springsteen, "The Boss" himself, and Jon Bon Jovi warmed up the crowd on a night when temperatures dipped near the freezing mark.
"Let's all do our part so we can look back on 2016 and say we stood with Hillary Clinton on the right side of history," Springsteen said.
The Boss, whose music has long championed working-class Americans, denounced Trump as "a man whose vision is limited to little beyond himself."
Organisers did not remove the presidential seal from the podium used by Obama when Clinton spoke, as would normally be done - optics are everything.
After the rally, Obama headed back to Washington and Clinton headed to Raleigh, North Carolina, another key battleground, for a midnight rally, the last of the day.
Clinton - who has been joined by A-listers from Beyonce and Jay Z to Katy Perry in recent days - added one last guest in Raleigh: Lady Gaga.
Clinton said she will vote in the early morning at a school in Chappaqua.
Five states in one day, addressing euphoric crowds of thousands - Donald Trump reluctantly brought to a close an exhilarating and extraordinary 511-day election campaign that has upended America.
If he wins the White House on Tuesday, it's a roadshow that Americans can only expect more of: his unique blend of showmanship, eye-raising insults of his opponents and hyperbolic promises of salvation.
The 70-year-old man who has joked about taking a long vacation if he doesn't win must be exhausted, but the Republican reveled Monday in the adulation of crowd after crowd as he battled to the very last minute to pull off a shock upset against Democrat Hillary Clinton.
"Dream big because with your vote, we're just one day away from the change you have been waiting for your entire life," he bellowed to around 10,000 supporters in Manchester at his penultimate rally.
Republican presidential candidate Donald Trump surrounded by members of his family and vice presidential nominee Mike Pence, Nov. 7, 2016, in Manchester, N.H. (AAP)
"We are going to win the great state of New Hampshire, and we are going to win back the White House!" he cried -- his rallying cry the same at each rally, just tailor-made for the state of the moment.
With the wildest presidential race in generations nearly in the rear-view mirror, Trump has stalked battlegrounds and Democrat-leaning states, desperate to persuade Americans they would be better served by a political outsider than establishment favorite Clinton.
"Our failed political establishment has delivered nothing but poverty, nothing but problems, nothing but losses," he told 5,000 people in Raleigh, North Carolina, reducing the essence of his long and controversial campaign into a handful of soundbites.
He began his day of reckoning in the make-or-break state of Florida-- vital to his White House hopes.
"My poll numbers are going through the roof," he said in Sarasota, his hyperbole increasing as the clock ticked down.
At each campaign stop, Trump insisted he is doing better than polls suggest, proclaiming his support among African Americans and Latinos, despite scant evidence of significant minority presence at his rallies.
Ever the populist, if easily distracted, he called on one supporter wearing a rubber, Halloween-style Trump mask to hand it over.
"Nice head of hair, I'll say that," Trump reflected as he held the mask close to his face, photographers eagerly snapping away.
Obama won North Carolina in 2008 but lost it four years later. Trump holds the narrowest of leads in the southern state.
Clinton was aiming to claw back some of that ground by holding a high-profile midnight rally in Raleigh late Monday, with pop star Lady Gaga in tow.
North Carolina's Republican governor, Pat McCrory, acknowledged to AFP that the race in his state now was "all based upon turnout."
Trump has jibed at suggestions that celebrities performing for Clinton would get people to the polls.
He railed against the "language" used by Jay-Z at a Clinton rally in Ohio and, after rock legend Bruce Springsteen performed in Philadelphia, said it was "demeaning" to the political process to listen to a musician, saying that Clinton alone "can't fill a room."
And then rocker Ted Nugent played before Trump's last rally in Michigan.
Trump jetted into Manchester from the Pennsylvania Rust Belt city of Scranton, where Clinton's father was born but where the Republican is counting on the blue-collar working class. Before that, it was Raleigh.
Clinton pulled out all the stops in Pennsylvania with a mega-event of her own, that her campaign said drew 40,000 people featuring the Obamas, ex-president Bill Clinton, Jon Bon Jovi and Springsteen.
But if there were no celebrities in Manchester, other than Trump, his photogenic adult children and his announcement that he had the vote of American football star quarterback Tom Brady, supporters gathered more than eight hours ahead of schedule, bringing snacks and fold-out chairs.
"The energy is just going to be amazing," said first-time voter Jack Keefe, 18, who took off school in neighboring Massachusetts to drive 90 minutes to see Trump, whom he views as a role model.
"I think that if he loses, I've just got to pray that Hillary Clinton isn't as bad as I think she is."
Trump was to wrap up his whirlwind day in Grand Rapids, Michigan, a state where Clinton is ahead in polling.
Trump's campaign nevertheless insists the race there is tied, and that voter enthusiasm could put Trump over the top.
But in New Hampshire, fist pumping and clapping his hands, grinning from ear to ear and pointing to the crowd he appeared, unable, it seemed to tear himself away.
"I'm really happy I did this. It's been an amazing experience," he said with something akin to wistfulness.
Trump's vow to rip up America's free trade deals, build a wall on the Mexican border and renegotiate US treaty alliances has spooked world markets seeking stability after the recent global slowdown.
Last week, US stocks as measured by the S&P 500 index fell for nine straight days for the first time since 1980, only to recover a little when the FBI confirmed Clintonwould not face prosecution over her emails.
Global stock markets surged on Monday, with Wall Street gaining more than two percent, as hopes for a Clinton victory rose after FBI director James Comey's weekend announcement that she was in the clear.
The dollar also gained, and analyst Patrick O'Hare of briefing.com said: "You can certainly take for granted from today's rally that the market seems to like the idea of Mrs. Clinton being elected president."
On the eve of the vote, Clinton held a widening but still close 3.4 percentage point lead over Trump in a four-way race including two fringe candidates, according to a RealClearPolitics average of national polls.
But a win in votes casts will mean nothing if she does not win the electoral college, fending off a last-ditch Trump bid to secure Florida and poach North Carolina, Michigan, Ohio, Nevada or New Hampshire.
On the eve of voting, respected data journalist Nate Silver's site FiveThirtyEight.com gave the Democrat a 71 percent chance of victory, conservative odds compared to newer rivals.