MANHEIM, Pa. (Reuters) - Republican presidential nominee Donald Trump closed out a rough week for his campaign on Saturday by escalating personal attacks on Democrat Hillary Clinton, questioning her stamina and saying she should be in prison for her handling of classified emails.

After a week in which he drew wide criticism for a public feud with a former beauty queen, Trump sought to rebound with a highly negative attack on his opponent in the Nov. 8 election, with a second presidential debate against her looming in a week.

At the same time, the New York Times reported it had obtained records showing Trump declared a $916 million loss on his 1995 income tax returns, a deduction so large that it may have allowed him to avoid paying any federal income taxes for years.

Trump has refused to release his tax records, saying he is under a federal audit.

At a rally in Manheim, Pennsylvania, Trump said he did not believe Clinton, who suffered a bout of pneumonia last month, was up to the task of being president. He tried to resurrect a tactic he employed against former Republican rival Jeb Bush, who Trump had derided as “low energy.”

Clinton kept her pneumonia diagnosis private until she was seen nearly collapsing while getting into her vehicle at a ceremony marking the Sept. 11, 2001, attacks in New York.

Ticking off a list of world problems, Trump said, “She’s supposed to fight all of these things and she can’t make it 15 feet to her car. Give me a break.”

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“Folks, we need stamina, we need energy, we need people who are going to turn deals around,” Trump said.

Trump has often told crowds who chant “lock her up” over her use of a private email server as U.S. secretary of state from 2009 to 2013 to instead help him defeat her.

But on Saturday, Trump told thousands of supporters that Clinton’s handling of classified emails and destroying of 33,000 emails that she had deemed of a personal nature meant that “she should be in prison, let me tell you.”

Trump did not stop there. He said he did not believe Clinton would be loyal to her supporters and chuckled, “I don’t even think she’s loyal to Bill, to tell you the truth. And why should she be, right? Why should she be?”

In 1998, Clinton’s husband, former President Bill Clinton, was caught up in a sex scandal involving former White House intern Monica Lewinsky.

Trump was widely seen as having lost his first presidential debate with Clinton last Monday although he cites online polls showing he won.

In the days since the debate, Trump has been struggling to regain his footing, getting caught up in a back-and-forth with former Miss Universe Alicia Machado, who Trump had criticized for gaining weight.