PHOENIX (Reuters) - Sensing a potential turning point, Republican presidential nominee Donald Trump mounted a furious effort on Saturday to portray Democrat Hillary Clinton as unfit to lead the country after the latest chapter in her email controversy unfolded as he tries to mount a comeback.

With the Nov. 8 election only 10 days away, Trump devoted much of his stump speech to try to take the maximum advantage of the FBI’s disclosure that it is investigating more emails as part of a probe into Clinton’s use of a private email server.

Little is known about the extent and focus of the new FBI review. But Trump was quick to declare his rival “guilty” at rallies in Phoenix and in Golden, Colorado, declaring that she is symbolic of a type of public corruption that is a “grave threat to our democracy.”

Trump charged that the Justice Department, populated by appointees of Democratic President Barack Obama, is trying to help Clinton, given news reports that top department officials did not want FBI Director James Comey to reveal his new review.

“When the outcome is fixed, when the system is rigged, people lose hope. They stop dreaming. They stop trying,” Trump said in Phoenix. “Hillary Clinton’s corruption is corrosive to the soul of our nation and it must be stopped.”

Clinton herself has repeatedly attacked Trump as not fit to be president.

The new uproar could not have come at a more opportune time for Trump, who has been reeling for weeks from the release of a 2005 audio tape in which he boasted about groping women and the emergence of a host of women who said he did just that to them.

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Trump has narrowed the gap in public opinion polls between him and Clinton nationally and in some battleground states where the election is likely to be decided. But most analyses of the polls show him facing a defeat, perhaps a landslide, if the election were to be held today.

That made it essential for Trump to try to change the subject from his own setbacks and focus on those of Clinton, and give establishment Republicans who have been reluctant to support him a reason to get behind him, and perhaps sway some undecided voters as well.

Still, the Phoenix rally provided a reminder why some Republicans cannot bring themselves to support Trump, as a man there taunted reporters with a chant of “Jew S. A.” when the rest of the crowd was chanting “USA.”

Trump’s next couple of days on the campaign trail reflect a change in strategy with uncertain rewards. He is to campaign in Albuquerque, New Mexico, on Sunday and in Michigan on Monday, two states that have voted Democratic in recent presidential elections and appeared poised to do so again.