MIAMI, United States (AFP) – Donald Trump stepped up his attacks against Hillary Clinton, seeking to exploit the FBI’s decision to reopen an investigation into her emails, as America’s bruising election campaign heads into its final stretch.

Just 10 days before the country goes to the polls to elect either the former US secretary of state or the bombastic Republican billionaire, America’s top cop James Comey has been thrust center stage. 

The FBI director wrote to lawmakers on Friday, announcing that his agents are investigating a newly discovered trove of emails, renewing an enquiry that the Clinton campaign thought ended in July.

Trump pounced. Campaigning in the western state of Colorado, which has been leaning toward Clinton, he denounced what he called his opponent’s “criminal and illegal conduct,” to chants of “Lock her up!”

“This is the biggest political scandal since Watergate, and it’s everybody’s deepest hope that justice at last will be beautifully delivered,” Trump, 70, told a later rally in Phoenix, Arizona.

While his 69-year-old opponent remains on course to be voted in as America’s first female president at the ballot box on November 8, her campaign is furious that its momentum has slowed in the final straight.

Clinton campaigned hard in the key battleground state of Florida on Saturday, greeting thousands of supporters at a Jennifer Lopez concert in Miami after earlier demanding that Comey explain in detail why he had effectively reopened the inquiry declared complete in July.

“It’s pretty strange to put something like that out with such little information right before an election,” she said in Florida’s coastal town of Daytona Beach.

“In fact, it’s not just strange, it’s unprecedented and it is deeply troubling because voters deserve to get full and complete facts,” she added.

“So we’ve called on Director Comey to explain everything right away, put it all out on the table, right?” she declared, to rapturous cheers.

– Never back down –

In reality, it seems unlikely that much progress will be made in the investigation before polling day and few observers expect Clinton to face criminal charges. 

But every day that she spends dealing with the fallout of her decision to use a private email server as secretary of state is a day the media is not dwelling on the scandals dogging Trump.

On Saturday, a poll of polls by tracker site RealClearPolitics put Clinton 3.9 percentage points ahead of the Republican nationwide, down from 7.1 points just 10 days previously.

But despite narrowing polls, an election model published daily in the New York Times and based on various state and national surveys on Sunday gave Clinton a resounding 91 percent chance of winning the presidential vote. 

Trump — himself dogged by scandal over alleged sexual misconduct and accusations from at least 12 women — has relished the email probe.

“Hillary Clinton’s corruption is corrosive to the soul of our nation, and it must be stopped,” the real estate tycoon said in Arizona.

On Saturday he also received the public endorsement of the father of 26-year-old aid worker, Kayla Mueller, who was kidnapped in Syria in August 2013 and killed in a 2015 coalition air strike.

Across the country at the Lopez concert, Clinton embraced the hit singer on stage and accused her opponent of stoking fear, disgracing American democracy and insulting “one group of Americans after another.

“Are we going to let Donald Trump get away with that? You’re right. We’re not,” she said. “No matter what they throw at us, we don’t back down. Not now. Not ever,” the Democrat said.