The Washington Post has a very revealing quote for those who are breathlessly awaiting Robert Mueller’s appearance on the Hill.

The paper talked to his longtime deputy at the FBI, John Pistole, who was quick to tamp down expectations.

“For anybody hoping he’s going to provide new information or evidence against the president, I think many people will be very disappointed,” Pistole said.

He also noted that “on the other side of the aisle, some may be disappointed to find out that he’s not a demagogue of the left.”

The media drumbeat is growing louder as the former special counsel prepares for five hours of House testimony on Wednesday, divided between the Judiciary and Intelligence panels.

But I’ve felt from the beginning that the pundits are inflating a giant hot-air balloon that is likely to be pricked when Mueller is sworn in.

Simply put, he is a reluctant witness, appearing only under the threat of subpoena.

And the man who said “the report is my testimony” is not going to be volunteering a whole lot of opinions.

Mueller will be “as unresponsive as possible, while telling the truth,” Pistole says.

Indeed, Mueller's spokesman confirmed more diplomatically that "you can expect him to stick pretty close to the four walls of the report come Wednesday.”

President Trump is already offering pregame commentary, tweeting: “Highly conflicted Robert Mueller should not be given another bite at the apple. In the end it will be bad for him and the phony Democrats in Congress who have done nothing but waste time on this ridiculous Witch Hunt. Result of the Mueller Report, NO COLLUSION, NO OBSTRUCTION!”

(Mueller actually said he could not reach a conclusion on whether there was criminal obstruction because of DOJ guidelines against indicting a sitting president.)

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Another POTUS tweet covers territory that Republicans undoubtedly will pursue over whether Mueller’s probe was biased: “But the questions should be asked, why were all of Clinton’s people given immunity, and why were the text messages of Peter S and his lover, Lisa Page, deleted and destroyed right after they left Mueller, and after we requested them(this is Illegal)?”

Speaking to reporters yesterday, Trump again invoked what he views as Mueller’s conflicts, including his past relationship with another former FBI chief.

“His best friend is Comey,” Trump said.

He said Mueller had conflicts with him stemming from an old business relationship (involving fees at a golf club) and because he wanted to be FBI director again (he met with the president at Trump’s request).

But Trump did say he had “respect” for Mueller for reaching the findings he did despite these alleged conflicts.

The Democrats are well aware that Mueller will not be effusive. But they have this vision that if they can just get him to read from the report, perhaps sprinkled with some added comments, it will have a major impact on public opinion.

In this view, most Americans haven’t read his 448-page report because they’re too busy, lazy or dumb—and will be shocked and appalled when they hear what’s in it.

But they’ve also been exposed to an avalanche of media coverage of the report, which does contain sections that are damaging to the president.

Yet given our polarized culture, how many minds are likely to be changed, in either direction, about Donald Trump’s culpability in a probe that led to no charges?

House Judiciary Chairman Jerry Nadler said on “Fox News Sunday” that it was important for him to summon Mueller because “the report presents very substantial evidence that the president is guilty of high crimes and misdemeanors.”

So the man running the hearing is making no secret of the fact that he clearly favors impeachment.

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The hearings are being billed as the last chance for the Democrats to rekindle fading public interest in the Mueller investigation.

But that moment has probably passed.