Steve Bannon says supporters will turn when tax records reveal Trump's 'just another scumbag': Michael Wolff

President Donald Trump's former chief strategist believes a thorough investigation will reveal his family business is a "semi-criminal enterprise" -- and ultimately end his presidency.

The president is fighting congressional orders to turn over his tax returns, putting Treasury Secretary Steve Mnuchin in possible legal peril, and former White House chief strategist Steve Bannon said Trump has every reason to fear their release, according to excerpts from a new book reported by The Guardian.

“Trump was vulnerable because for 40 years he had run what increasingly seemed to resemble a semi-criminal enterprise,” wrote author Michael Wolff in his forthcoming book, "Siege."

Bannon, who is quoted extensively in this book and Wolff's previous White House tell-all, "Fire and Fury," takes that even further.

“I think we can drop the ‘semi’ part," Bannon told Wolff.

Bannon said investigations into Trump's finances will eventually cause his strongest supporters to turn on the president, when they realize he's not nearly as wealthy as he claims to be.

In Siege, Wolff quotes Bannon saying investigations into Trump’s finances will cut adrift even his most ardent supporters: “This is where it isn’t a witch hunt," Bannon said. "Even for the hard core, this is where he turns into just a crooked business guy, and one worth $50 million instead of $10 billion."

“Not the billionaire he said he was," Bannon added, "just another scumbag.”