After two weeks of sabre-rattling at their back-to-back party conventions, Donald Trump and Hillary Clinton have formally kicked off their three-month presidential campaign, with the former threatening to take the gloves off and the latter hoping to neutralise the offence with a new-found momentum.

Under a ceaseless attack for four days from the entire Democratic establishment, Trump announced that he is all set to return the fire. Hopping across to Colorado, the New York billionaire, derided by President Barack Obama as a “homegrown demagogue”, sought to tell Clinton that he won’t play “Mr Nice Guy” any more.

Clinton herself, accompanied by husband Bill and her vice-presidential running mate Tim Kaine, began a bus tour of Pennsylvania and Ohio, two of a handful of critical battleground States that will decide the presidential race.

Dismissing Clinton’s acceptance speech as “so average”, Trump has sought to specifically target her on national security, jobs and taxes, attacking her for not making any reference to the dangers posed to America by radical Islamic terrorism.

“Hillary’s refusal to mention Radical Islam, as she spushes a 550 per cent increase in refugees, is more proof that she is unfit to lead the country,” Trump said in a series of tweets. “Our way of life is under threat by Radical Islam and Hillary Clinton cannot even bring herself to say the words,” he said.

Questioning her assertions that she will reform Wall Street and see to it that the big corporations pay their fair share of taxes, Trump said she will do nothing of the kind since “she is owned by Wall Street”.

The Trump campaign sought to dismiss Clinton’s speech as an “insulting collection of clichés and recycled rhetoric”, saying: “She spent the evening talking down to the American people she’s looked down on her whole life.”

In a new video, the Trump campaign claimed: “In Hillary Clinton’s America, things get worse. Under her dishonest plan: Taxes keep rising. Terrorism spreads. Washington insiders remain in control. Americans, losing their jobs, homes - and hope.”

Clinton herself kept firing salvoes at Trump, saying that for his claims about making America great again, the billionaire businessman “doesn’t make a thing in America except bankruptcies”.