– Democrats want incriminating, hidden-till-now details about Donald Trump and Russia. Republicans want Robert Mueller to concede it was all a waste of time and money, if not an outright hoax.

Neither side is likely to get just what it wants Wednesday, but the former special counsel's first open testimony on his investigation has Washington and the rest of the political world in a high state of anticipation just the same.

Here are some things to look for when Mueller appears before the House Intelligence and Judiciary Committees to answer questions about his investigation into Russian interference in the 2016 election and possible cooperation with the Trump campaign.

Much of Mueller's report focuses on the question of whether Trump obstructed justice, and Democrats on the Judiciary Committee say that's where their attention will be, too. And for good reason: His report examines in blow-by-blow detail nearly a dozen episodes in which the new president sought to control the Russia probe, narrow its scope or even have investigators fired.

Democrats said they expect to draw Mueller out in several of these areas. They include Trump's demands that then-White House Counsel Don McGahn press for Mueller's firing and his push to have former Attorney General Jeff Sessions limit the investigation to future election interference rather than past conduct.

The afternoon session before the Intelligence Committee is likely to dwell more on Mueller's investigation into whether the Trump campaign coordinated with Russia to sway the outcome of the election. Mueller found insufficient evidence of a criminal conspiracy there, but he did leave open the question of whether Trump illegally stymied the investigation.

Mueller the Marine

Expecting Mueller to stray outside his report and drop scintillating details you have never heard before? Well, don't.

Mueller, an ex-Marine with a famously taciturn style, never relished his congressional appearances in his 12 years as FBI director — and this will be no exception.

He cautioned lawmakers in May that he would not go beyond the pages of his report if called upon to testify.

The Justice Department expects him to fulfill that commitment and to also steer clear of discussing the redacted portions of the report or the behavior of people who were investigated but not charged.

That means he's unlikely to answer certain critical questions, including whether he would have recommended indicting Trump himself if Trump had not been president of the United States. That question matters since Mueller cited Justice Department legal opinions that say a sitting president cannot be charged in explaining his decision to not reach a conclusion on whether Trump had broken the law.

Mueller's not one for hypotheticals, though, so it's fair to assume he won't engage Democrats on that one.

The 'snitty' letter

Mueller will almost certainly be pressed about tensions with Attorney General William Barr over the way his report was handled and how the Justice Department communicated its findings to the public, including the attorney general's decision to exonerate the president even when the special counsel pointedly did not do so.

Mueller complained privately to Barr in March that the attorney general's four-page letter summarizing the main findings of his report "did not fully capture the context, nature and substance of this office's work and conclusions." Barr, in turn, has called Mueller's note "a bit snitty."

Mueller has made clear he didn't think it was appropriate to make a determination one way or the other about whether the president had committed a crime. He has rejected Barr's assessment that the evidence couldn't satisfy an obstruction of justice allegation, noting both in his report and again in a public statement from the Justice Department podium that if he had confidence the president had not committed a crime, he would have said so.

Barr had no such hesitation and has said Mueller shouldn't have started investigating the president if he wasn't prepared to reach a conclusion.

Mueller probably doesn't want to extend a public war of words with Barr, a longtime friend and his former boss. But he will very likely be asked about the dispute, and he may have a hard time getting around it.

The dossier

Republicans aren't likely to directly attack Mueller himself. The former special counsel is a decorated Vietnam War veteran who steered the FBI through the Sept. 11 attacks and was appointed by a Republican president to run the storied law enforcement agency.

But that doesn't mean they won't have areas to mine.

They are likely to seize on the origins of the investigation and press Mueller on the extent to which the FBI, in the early weeks and months of its Russia probe, relied on information from a dossier of anti-Trump research paid for by Democrats. The Justice Department has acknowledged that the dossier helped form the basis of a secret surveillance warrant it obtained to monitor the communications of a Trump campaign aide, though the investigation had actually begun months earlier and was based on entirely separate allegations.