Speaking to reporters aboard her plane Sept. 5, Democratic presidential candidate Hillary Clinton said she's "taken aback" by revelations about Donald Trump's foundation's gift to a political group connected to Florida Attorney General Pam Bondi. (Video: The Washington Post/Photo: Melina Mara)

Hillary Clinton escalated her attacks on Donald Trump’s character and qualifications for the presidency Tuesday, seizing on renewed scrutiny of an improper political donation that Trump made to Florida’s attorney general as she accused him of concealing “scams.”

The Democratic presidential nominee called on her rival to reveal details about his communication with Florida Attorney General Pam Bondi (R), to whom Trump made a $25,000 political contribution in 2013 as Bondi was considering investigating claims against Trump University, the embattled for-profit education business. Critics say the donation crossed ethical lines.

“Of course, as we know, there was a phone conversation between them. They contradict each other. The American people deserve to know what was said, because clearly the attorney general did not proceed with the investigation,” Clinton told reporters Tuesday during a ­question-and-answer session on her campaign plane.

“The list goes on and on: the scams, the frauds, the questionable relationships, the business activities that have stiffed workers,” Clinton said later as she renewed her call for Trump to release his tax returns and “come clean.”

Trump lobbed attacks of his own. In an interview with ABC that aired Tuesday, Trump scrutinized Clinton’s appearance. “Well, I just don’t think she has a presidential look, and you need a presidential look,” he told ABC’s David Muir.

Republican presidential nominee Donald Trump slammed the Iran nuclear deal calling it one of the "dumbest" he's ever seen. Speaking to veterans at a campaign event in Virginia, Trump said, "This is a deal crooked Hillary Clinton wanted ... The deal with Iran was at the highest level of incompetence." (Reuters)

Trump also knocked Clinton during a campaign event in Greenville, N.C., on Tuesday evening over her use of a private email server as secretary of state.

“She fails to meet the minimum standard for running for public office. If she applied for a low-level job at the State Department today, just a low-level job, she couldn’t even get a security clearance based on what she’s done,” he said. “Her conduct is disqualifying.”

“People who have nothing to hide don’t smash phones with hammers . . . or destroy evidence to keep it from being publicly archived as required under federal law,” he added.

The intensified and highly personal attacks come as the rival campaigns enter the crucial window between Labor Day and Election Day. And they followed a round of polls for Clinton suggesting that the national advantage she has held for much of the summer has diminished slightly.

Between personal barbs, the two also questioned each other’s national security credentials throughout the day, ahead of a forum in New York on Wednesday at which Clinton and Trump are scheduled to appear back to back on MSNBC and NBC to discuss issues that will confront the country’s next commander in chief.

Trump held a town hall gathering on national security issues in Virginia Beach on Tuesday afternoon. The event, attended by retired Lt. Gen. Michael T. Flynn, an ally and adviser, came on the heels of an announcement by Trump’s campaign that he had been endorsed by 88 retired senior military officials. During the Virginia Beach event, Trump mocked Clinton’s ability to negotiate with world leaders.

“You know, Hillary likes to play tough with Russia. Putin looks at her and he laughs. Okay? He laughs. Putin looks at Hillary Clinton and he smiles. Boy, would he like to see her,” Trump said. “That would be easy, because look at her decisions.”

The candidate later attended a roundtable with military families where he was joined by his daughter Ivanka, Flynn and former New York mayor Rudolph Giuliani.

At a campaign rally in Tampa, Clinton knocked Trump’s national security credentials and touted her own experience as secretary of state and as a U.S. senator representing New York. She said Trump often has “no clue” what he’s talking about on military issues and pointed to statements he has made about fighting the Islamic State militant group that she said “have been all over the map.”

“He says he has a secret plan to defeat ISIS, but the secret is he has no plan,” Clinton told a crowd estimated at 1,500 at the University of South Florida, which is located in a community with sizable active-duty and military veteran populations. ISIS is another name for the Islamic State.

The Clinton campaign has repeatedly attacked Trump over his grasp of foreign policy issues, scrutinizing his temperament in an effort to raise questions about how he would conduct international diplomacy. Clinton has regularly noted on the campaign trail that the Republican foreign policy establishment remains deeply uneasy with Trump and has pointed to many conservative foreign policy experts who have endorsed her.

Ahead of Wednesday’s forum, the Clinton campaign also released a new television ad seeking to highlight what it characterized as Trump’s “continued disrespect” for the military and veterans. The spot features veterans, including former senator Max Cleland (D-Ga.), reacting to disparaging comments Trump has made.

The Trump campaign fired back, pointing to Clinton’s narrowing lead and accusing her of failing to campaign aggressively enough in August.

“Hillary Clinton’s remarks today in Tampa are exactly what you would expect to hear from a candidate who took off the month of August and woke up in September losing the election,” Trump’s senior communications adviser said in a statement Tuesday.

Clinton told reporters that sometimes Trump gets a pass because people have grown to expect less from him. During that media gaggle, she said that Trump should “come clean” about his finances and that she would continue to press the Republican to release his tax returns until Election Day, declaring that “he clearly has something to hide.” She ticked off a list of what she characterized as questionable aspects of Trump’s finances, including the multiple times his companies have declared bankruptcy, repeated accusations of “fraudulent behavior,” hundreds of millions of dollars in business debt and continuing controversy over Trump University.

“Clearly his tax returns tell a story that the American people deserve and need to know,” Clinton said. “I’m going to continue to raise this, because I think it is a fundamental issue about him in this campaign.”

The renewed scrutiny of the Bondi contribution could be a political liability for Trump, even as Clinton’s family foundation faces scrutiny over her communications with top donors while she was secretary of state.

Trump told reporters Monday that he had not engaged in quid pro quo. But the timeline has left his critics and watchdog groups accusing him of impropriety.

The donation, made by the Donald J. Trump Foundation, went to a pro-Bondi political organization days after her office disclosed that it was looking into Trump University. Bondi ultimately decided not to open an investigation, prompting scrutiny from critics and local media at the time. And the contribution also violated restrictions preventing charities from making political donations to candidates.

The Trump foundation recently paid a $2,500 penalty for failing to disclose the political donation to the Internal Revenue Service.