If Democrats hoped Wednesday's high stakes hearings with the former special counsel Robert Mueller would help them shore up public support for President Donald Trump's impeachment, they likely came away sorely disappointed.

Mueller frustrated both sides of the aisle with his repeated refusal to answer questions about his findings, the origins of the Russia investigation, his relationship with the attorney general, and other topics related to the probe.

"Mr. Mueller is being consistent," Rep. Al Green, the first Democrat to call for Trump's impeachment, told INSIDER. "He's doing what was anticipated — at least, what I anticipated."

That said, Democrats did notch a few victories: Mueller excoriated Trump for praising WikiLeaks, he contradicted Trump on a key claim under oath, and he pointedly told lawmakers that elected officials should be held to a higher standard than "mere avoidance of criminality."

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The stakes for Democrats could not have been higher when the former special counsel Robert Mueller took center stage on Capitol Hill Wednesday morning. That's why it was all the more painful for them when Mueller's highly anticipated testimony fell significantly short of their expectations.

Mueller appeared before the House judiciary and intelligence committees for two back-to-back hearings. The first, before the judiciary, focused primarily on Mueller's findings in the obstruction of justice investigation into President Donald Trump.

The second, which took place before the intelligence panel, zeroed-in on Mueller's counterintelligence findings in the FBI's Russia investigation; namely, the nature of Russia's interference in the 2016 US election and whether members of the Trump campaign coordinated with Moscow's efforts.

Before the hearings even kicked off, Democrats were urging caution.

Read more: 'The death rattle for impeachment': Republicans take a victory lap after Mueller's testimony misses Democrats' expectations

The worst case scenario, one Democratic House aide told the Washington Post early Wednesday, is "that it's a snooze-fest and we put in all of this work and effort for nothing. [Constituents] will be really bummed when they learn nothing new [today]."

"Everyone will watch it and nothing will happen," the aide added.

'Mr. Mueller is being consistent'

To be sure, the former special counsel frustrated both sides of the aisle with his repeated refusal to answer questions about his findings, the origins of the Russia investigation, his relationship with the attorney general, and other topics related to the probe.

Instead, he told lawmakers, "I would direct you to the report."

When asked about issues that were not contained in the 448-page document, Mueller said, "I'm not going to discuss other matters."

"Mr. Mueller is being consistent," Rep. Al Green, the first Democrat to call for Trump's impeachment, told INSIDER. "He's doing what was anticipated — at least, what I anticipated."

Read more: 'Problematic is an understatement': Mueller excoriates Trump for praising WikiLeaks during the 2016 election

Indeed, when Mueller gave his first public statement on the Russia investigation in May, he said he would not testify before Congress because "the report is my testimony." He added that if he were subpoenaed — which he was — he would not go beyond stating what was publicly revealed in the report.

"I don't think it was necessary to have this hearing," Green said. "I do believe that it's always good to have transparency, but I don't think you have to have this hearing, given that Mr. Mueller has given us a roadmap to impeachment. But it's styled, 'Mueller Report.' If he had styled the report, 'Roadmap to Impeachment,' we wouldn't be having this hearing."

Mueller's report said prosecutors did not find sufficient evidence to establish a criminal conspiracy between the Trump campaign and the Russian government related to 2016 election interference. In the obstruction case, Mueller declined to make a "traditional prosecutorial judgment," citing Justice Department guidelines that bar prosecutors from indicting a sitting president.

However, the former special counsel laid out an extensive set of obstruction evidence against Trump, and prosecutors noted that if they had confidence that the president did not commit a crime, they would have said so.

They also explicitly stated that their report "does not exonerate" Trump.

Read more: Mueller says he didn't subpoena Trump because he expected Trump to fight it and wanted to expedite 'the end of the investigation'

Prosecutors added that the constitutional remedy for accusing the president of wrongdoing does not lie with the Justice Department — a line many lawmakers believe to be a reference to Congress' impeachment powers. Moreover, they said a president is not immune from criminal prosecution once he leaves office, and Mueller reiterated as much during Wednesday's testimony.

' Bob Mueller is struggling '

For those who read Mueller's report, his findings painted a damaging portrait of a campaign that repeatedly welcomed foreign interference in the election and, later, a besieged president whose attempts at obstructing justice were unsuccessful largely because his own aides refused to carry out his orders.

But the problem Democrats faced leading up to Wednesday's hearing was that the majority of Americans hadn't read the document. They hoped that they could have the man who wrote the report bring it to life and, in doing so, drum up public support for impeachment.

Predictably, Mueller didn't give them what they wanted.

"He was clearly a reluctant and tentative witness, and wanted to say as little as he could beyond the report," Julian Epstein, a former Democratic general counsel for the House Judiciary Committee, told Politico.

"Anyone who knows Bob Mueller is not the least bit surprised by his reticence today," one former senior Justice Department official who worked closely with Mueller when he was FBI director, told INSIDER. "He's a prosecutor to the core — and he warned everyone he wouldn't go beyond what was contained in his report because the report is his testimony."

The Democrats' case was also complicated by the fact that Mueller has been away from the public domain for several years and appears to be out of practice with answering pointed questions from lawmakers.

According to Politico, Mueller asked lawmakers to repeat their questions 30 times. He said he wasn't familiar with the so-called Steele dossier, he said he did not recall who Corey Lewandowski — the former Trump campaign manager mentioned several times in Mueller's report — was, he messed up on a question about his prior experience, and he gave an answer which he later had to go back and correct.

"Bob Mueller is struggling," Glenn Kirschner, a former federal prosecutor who worked under Mueller in the US attorney's office in Washington, DC, wrote on Twitter. "It strikes me as a health issue. We need only look at footage of his earlier congressional appearances to see the dramatic difference in his demeanor and communicative abilities."

Democrats notch a few victories

That said, Democrats did gain some capital.

In one of his sharpest public critiques of the president to date, Mueller excoriated Trump for his effusive praise of WikiLeaks.

"Well," Mueller said, "problematic is an understatement in terms of what it displays in terms of giving some hope, or some boost, to what is and should be illegal activity."

At another point, when House Intelligence Committee Chairman Adam Schiff asked Mueller whether the Trump campaign built its "strategy [and] messaging strategy, around those stolen documents," Mueller responded, "Generally, that's true."

"And then they lied to cover it up?" Schiff asked.

"Generally, that's true," Mueller repeated.

Mueller also pushed back on Trump's characterization of his investigation, telling Schiff, "It is not a witch hunt."

Trump also challenged Mueller on Twitter to testify under oath that he did not interview for the FBI director job one day before being appointed special counsel.

Mueller did just that, telling lawmakers that he went to the White House, but only because the president had requested his advice and input on who he should tap for the job after dismissing James Comey. The meeting, Mueller said under oath, "was about the job, but not about me applying for the job."

In another exchange with Rep. Val Demings that flew under the radar, Mueller suggested the president misled investigators in his written responses to questions.

"Isn't it fair to say [Trump's] written answers were not only inadequate and incomplete because he didn't answer many of your questions, but where he did, his answers show that he wasn't always being truthful?" Demings asked.

"Generally," Mueller responded.

And toward the end of the marathon hearings, Schiff asked the former special counsel, "We should hold our elected officials to a standard higher than mere avoidance of criminality, correct?"

"Absolutely," Mueller replied.