Donald Trump suggested Monday that one reason Hillary Clinton is running for president is to avoid incarceration.

The Republican presidential hopeful explained to supporters at a campaign rally in Springfield, Ill., that the scandal surrounding the private email server Clinton kept as secretary of state is "so much worse" than what others have been prosecuted for in the past. He named former CIA director, Gen. David Petraeus, as an example.

"People are in jail right now for doing five percent of what she did, and the Democrats are not going to prosecute her, and it's frankly a disgrace," Trump said during the rally.

"Hillary is running for a lot of reasons — one of 'em is because she wants to stay out of jail," he added.

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Trump also suggested that if the U.S. "had an honest government, Hillary wouldn't be allowed to run."

"If I win, we're going to look into that crime very, very seriously folks," he said.

Trump is fourth in the Washington Examiner's presidential power rankings. He will join 7 of his Republican rivals in Milwaukee Tuesday night for the fourth GOP prime-time debate.