PHILADELPHIA, United States (AFP) — With 101 days to go before Americans elect a new president, Donald Trump and Hillary Clinton will hit the campaign trail Friday hoping to secure a poll bump from their dueling party conventions.

In the last fortnight Republicans and Democrats have gathered to formally select their presidential nominees and tee-up what is already one of the most fractious and vitriolic presidential campaigns in living memory.

Both parties are deeply divided and led by profoundly unpopular figures with approval ratings below 40 percent.

Both conventions featured withering personal barbs, with Republicans in Cleveland chanting “lock her up” against Clinton and Democrats in Philadelphia painting Trump as an authoritarian and threat to US democracy.

Experts predict that “negative partisanship” — voting against a candidate, rather than for a candidate — will play a major role in deciding who makes it to the White House.  

Clinton, fresh from becoming the first woman in history to win the nomination of a major US political party, will take her vice presidential running mate Tim Kaine on a bus journey through Pennsylvania and Ohio.

The so-called “rustbelt” states are vital parts of almost any strategy to garner the 270 electoral college votes needed to win the presidency.

But in an election year that has seen the voice of the hard right and the hard left become louder and more shrill, Clinton is also making a bold play to seize the political center-ground.

A string of high profile Republicans, including the party’s last presidential nominee Mitt Romney, have publically stated they cannot vote for Trump because of his populist policies. This means some Republicans can be won over.

Accepting her party’s nomination, Clinton vowed to be a president for all Americans “for Democrats, Republicans, and Independents. For the struggling, the striving and the successful. For those who vote for me and those who don’t.”

On the convention floor, delegates waved bed-sized American flags and chanted “U.S.A.” in scenes of extreme patriotism more usually seen at Republican rallies.

Clinton also made a pitch for disgruntled working class voters, who have formed the backbone of Trump’s base.

In an hour-long primetime address, she laid out plans to boost the US economy, stressing that “my primary mission as president will be to create more opportunity and more good jobs with rising wages.”

Her efforts, she said, will focus particularly on places “that for too long have been left out and left behind, from our inner cities to our small towns, Indian Country to Coal Country.”

Trump meanwhile will be in Colorado, another battleground state, where his plan to build a wall on the Mexican border could resonate with angry white voters but turn Hispanic voters away in droves.

At the Republican convention Trump doubled-down on controversial far-right plans to stem Muslim and Hispanic immigration and get tough on crime.

“I have a message for all of you,” he told delegates. “The crime and violence that today afflicts our nation will soon, and I mean very soon, come to an end,” he said. “Safety will be restored.”

Both Clinton and Trump donated large chunks of invaluable convention time to softening their public image.

Both deployed family members to the frontline of that information war.

On Thursday Clinton’s daughter Chelsea described Hillary as a mother who took breaks from politics to read her “Goodnight Moon” and a grandmother Facetimes and reads “Chugga Chugga Choo Choo” to Chelsea’s daughter.

Trumps daughter Ivanka stepped out as a potent surrogate, trying to help his terrible approval among female voters by promising he would be a compassionate leader who would fight for women’s rights and affordable childcare.

While Trump himself portrayed a tough guy image, much of Clinton’s own address to Democrats was focused on tempering her image forged over decades of withering political trench warfare.

“Some people just don’t know what to make of me,” she said with a frankness that is unusual in American politics.

“The truth is, through all of these years of public service, the service part has always come easier to me than the public part.”

But addressing her reputation of putting prose before poetry, Clinton was unrepentant.

“It’s true,” she said. “I sweat the details,” be it the amount of lead permissible in drinking water or the cost of prescription drugs.

“It’s not just a detail if it’s your kid, if it’s your family,” she said.

Clinton and Trump will face off in their first presidential debate in late September.