WASHINGTON - White House frontrunner Hillary Clinton and Republican insurgent Donald Trump launched a final blitz to win votes in key battleground states Friday, slogging toward the end of America's divisive presidential campaign.

Clinton is slightly ahead in national polls as the nearly two-year race approaches its climax, with many Americans expressing relief that it will all be over in four days.

The nearly year-long US presidential race will come to a halt in New York on Tuesday as Hillary Clinton, the Democratic nominee, and her Republican rival Donald Trump-both confident of their chances-host parties a couple of miles apart in the heart of the city.

The New York Police Department (NYPD) is scrambling not only to keep the traffic flowing in one of the busiest swaths of New York, but they’re also putting the final touches on a plan to provide security at the two locations.

“It’s going to be a nightmare,” a high-ranking NYPD source said Thursday. “It’s definitely going to be a long night.”

Trump will be holding a victory celebration at the New York Hilton in midtown Manhattan, campaign staffers said.

Two of the most disliked candidates in US presidential campaign history are now focused on prodding lukewarm voters toward the polls - and using a stable of surrogates to make their cases.

Where enthusiasm is lacking, they are trying to manufacture it. Clinton will be in Cleveland later Friday for a rally featuring Jay Z and perhaps Beyonce, after stops in Pittsburgh and Detroit.

Trump meanwhile will make stops in New Hampshire, Ohio and Pennsylvania - all swing states.

The Manhattan billionaire's telegenic wife Melania made a rare campaign appearance Thursday, making a polite case for her husband and saying politics had gotten "too mean."

Both candidates are also saturating the airwaves with ads - mainly negative ones - and dialing the scare rhetoric up to fever pitch.

Clinton's campaign will reach a crescendo in Philadelphia on Monday, where she will appear with Bill Clinton and Barack and Michelle Obama - a union of Democratic Party A-list power.

Voters can expect not-so-subtle and not-so-gentle comparisons between Trump and the still-revered US founding fathers, who made their Declaration of Independence in the city, and later signed the US Constitution there.

The Clinton campaign on Friday rolled out a hard-hitting ad describing Trump's supposed first year in office.

"The video highlights what could happen if America elects someone so unqualified and unfit to be commander-in-chief, and what Trump's dangerous and divisive vision would mean for Americans," the campaign said.

Meanwhile, with little evidence, Trump has warned voters that the 69-year-old Clinton would be so busy fighting a possible FBI indictment that she effectively would not have time to run the country.

Pennsylvania voter Frank Behum, who spent 32 years working as an electrician for a steel plant before retiring, said the choice was not ideal. "You've got to pick the lesser of the two evils here," he said.

The campaigns are still jostling for supremacy in the handful of battleground states that will decide Tuesday's election.

Trump has the slenderest of leads in New Hampshire, is up 3.3 points in Ohio and trails by three points in Pennsylvania, according to poll aggregates compiled by RealClearPolitics.

North Carolina was in the eye of the political storm Thursday, with the candidates frantically crisscrossing the southeastern state.

The candidates' motorcades even passed one another on the tarmac at the Raleigh-Durham airport ahead of their rival rallies.

"You've got to get everyone you know to come out and vote," Clinton implored supporters in Raleigh, where she was joined by her onetime primary adversary Senator Bernie Sanders and "Happy" singer Pharrell Williams.

Trump has struggled amid boasts about sexual assault and allegations of groping by several women, but as the race nears its conclusion, profound Republican skepticism about his controversial candidacy appears to be ebbing.

"I think Republicans are coming home," Congressman Jason Chaffetz told CNN.

With the campaign in its final stages, Trump is sticking to the teleprompter and avoiding his most slanderous rhetoric. "Nice and cool. Right? Stay on point, Donald, stay on point," the 70-year-old said aloud during a Florida rally.

Trump may yet have some hope. A Chinese monkey described as the "king of prophets" has tipped him for the US presidency over the former secretary of state.