Steve Bannon provoked lots of chatter for telling Charlie Rose on "60 Minutes" that President Trump's firing of FBI Director James Comey may have been the worst mistake in "modern political history."

What's intriguing is the reason he said it: the belief of some close White House allies that special counsel Bob Mueller, whose appointment was triggered by Comey's ouster, could use events surrounding the firing to make an obstruction of justice case against Trump.

There's a good reason that Vice President Pence has hired a lawyer, Bannon freaked out about the decision, and Mueller plans to interview a slew of current and former West Wing aides: They were with Trump during those frantic days, and know what he was saying and what was on his mind.

White House aides with legal exposure to these events have quickly reached four conclusions, according to conversations with Jonathan Swan and me:

Mueller is burrowing in hard on the obstruction of justice angle. The "angry, meandering" draft White House justification for firing Comey — which was never released, but obtained by Mueller — could be used as evidence of Trump's unvarnished thinking when venting to staff. Legal fees, with white-collar attorneys charging $1,000 an hour, get cripplingly expensive pretty quick. Watch for outside legal defense funds to pop up quickly. The investigation's financial dimensions are worrisome. The focus on Michael Cohen, a Trump lawyer and confidant whose business dealings are intertwined with the president's, has been particularly troubling for those in Trump's close orbit. Cohen dealt with some colorful characters. And when plans for the Trump Tower in Moscow are fully picked apart, other questionable Russian characters may be drawn in.

Republicans close to the White House say every sign by Mueller — from his hiring of Mafia and money-laundering experts to his aggressive pursuit of witnesses and evidence — is that he's going for the kill.

The Wall Street Journal reports on the front page today that outside Trump lawyers "earlier this summer concluded that Jared Kushner should step down ... because of possible legal complications ... and aired concerns about him to the president." Kushner has since defended himself on Capitol Hill.

Be smart: Trump allies fret that the White House is ill-prepared for the public showdown with Mueller that will eventually come, and should be making legal, political and constitutional arguments for the president's right to fire Comey. Statements by Trump lawyers tend to rattle, rather than reassure, White House allies.

Trump associates tell me Trump mused about firing Mueller. But now, one associate said, the damage would be as horrendous as "firing the Pope."

P.S. Russian politician Vyacheslav Nikonov, a member of the Duma (ruling assembly), said on live TV that U.S. "intelligence missed it when Russian intelligence stole the president of the United States."