Donald Trump and his allies have a new argument against Hillary Clinton amid FBI's renewed probe into her emails

Donald Trump and his allies started to float a new line of attack this week against Hillary Clinton, after the FBI announced it had discovered new emails "pertinent" into its investigation of her private email server.

"I'm now convinced that we will be facing the very real possibility of a constitutional crisis with many dimensions and deleterious consequences should Secretary Clinton win the election," Trump said at a Michigan rally, Monday quoting an op-ed from Doug Schoen, a pollster for ex-President Bill Clinton who renounced his support of the Democratic nominee after the latest FBI revelation.

"She would be under protracted criminal investigation and probably a criminal trial, I would say," he said. "So we'd have a criminal trial of a sitting president."

The Republican nominee added that he believed that investigation will "last for years."

"Nothing will get done," Trump said. "I can tell you, your jobs will continue to leave Michigan. Nothing's going to get done."

Top Trump backers echoed these claims, even as FBI Director James Comey wrote in his bombshell Friday letter he "cannot yet assess whether or not this material may be significant."

Fox News host Sean Hannity, a devout Trump supporter, and former Rep. Jack Kingston of Georgia, a senior Trump adviser, both said the election of Clinton could lead to a "Constitutional crisis."

Former House Speaker Newt Gingrich went as far as to tell Hannity on his Monday television program that the new Clinton "campaign slogan" should be "vote Hillary and get Time Kaine for president."

Comey's letter to congressional leaders on Friday came just 11 days prior to the election. The FBI director has faced a barrage of attacks from prominent Democrats and political analysts for commenting on the agency's investigation.

At an Ohio rally on Monday, Clinton tried to reassure supporters that the FBI had "no case" against her.

"And first of all, for those of you who are concerned about my using personal email, I understand, and as I said, I am not making excuses," she said. "I have said it was a mistake and I regret it, and now they apparently want to look at emails of one of my staffers, and by all means they should look at them, and I am sure they will reach the same conclusion when they looked at my emails for the last year - there is no case here."