Republican presidential candidate Donald Trump gives a thumbs-up as he arrives at a campaign a rally in Clive, Iowa, on Sept. 13. (Evan Vucci/Associated Press)

CLIVE, Iowa -- Donald Trump attacked both Hillary Clinton and the Justice Department over her use of a private email server on Tuesday, saying that his Democratic rival's practices were more scandalous than Watergate and insisting that the Justice Department was tougher in investigating the explosive episode that brought down the presidency of Richard Nixon.

While the Republican nominee has compared Clinton's email use as secretary of state to Watergate before, his claim at a rally here that the Watergate-era Justice Department did a superior job to the current one drew scrutiny, since Nixon dismissed a special prosecutor probing the Watergate scandal after the top two Justice officials refused to do so. They resigned over the matter.

"This is far bigger and a far bigger scandal than Watergate ever was, but with Watergate we had Justice, we had a Justice Department that went after the people," he said. "Here’s something that just, nobody’s ever seen anything like this."

The Washington Post reported in October of 1973: "In the most traumatic government upheaval of the Watergate crisis, President Nixon yesterday discharged Special Prosecutor Archibald Cox and accepted the resignations of Attorney General Elliot L. Richardson and Deputy Attorney General William D. Ruckelshaus.

"The President also abolished the office of the special prosecutor and turned over to the Justice Department the entire responsibility for further investigation and prosecution of suspects and defendants in Watergate and related cases."

The incident is known as the "Saturday Night Massacre."

The current Justice Department conducted a criminal investigation into Clinton's personal email use and concluded that it would not charge her with any crimes. Trump and fellow Republicans have complained about what they say appears to be a lack of impartiality from the Obama administration. The nominee has said the lack of charges against Clinton is evidence of a "rigged system."

At the top of his remarks, Trump was interrupted by a protester demanding that he release his taxes, which he continues to keep shielded from the public. Meanwhile, as he has done repeatedly in recent days, Trump slammed Clinton for claiming that half of his supporters are a "basket of deplorables."

"Whether you vote for me or whether you vote for someone else, I will be still your greatest champion," Trump said.