After months of calling on special counsel Robert Mueller to testify about his investigation into Russian interference in the 2016 election, House Democrats’ wish is about to come true. Mueller, who has studiously avoided the political firestorm around his findings, will now appear in back-to-back public hearings before the House Judiciary and Intelligence committees on Wednesday.

The hearings have the potential to reignite the public debate about Mueller’s report, in which he pointedly said the president was not exonerated of obstruction of justice but didn’t say whether future prosecution or impeachment charges would be warranted. But the enigmatic special counsel is appearing reluctantly, only after House Democrats issued a subpoena demanding his appearance. So while an explosive televised hearing could help Democrats make the case that Trump is unfit for office, Mueller likely is not eager to help anyone make political hay out of his testimony — which means Democrats (and Republicans) will be on their own when it comes to crafting the narrative they want to emerge from the hearing.

It’s also been several months since Mueller’s report was released in April, which means there’s been plenty of time for people to develop opinions about the investigation’s conclusions. A lot will depend on how the hearings unfold, but polling shows that Democrats and Republicans are divided, so there’s also a very real question about how much Mueller’s testimony can actually move the needle. Democrats, for instance, are much more likely to approve of Mueller’s job performance than Republicans, and only Democrats support starting impeachment proceedings.

But even if the hearings don’t succeed in changing minds about the report’s findings — which, let’s face it, seems likely — hearing from Mueller could still energize Democrats and maybe help to weaken Trump’s approval rating as part of House Democrats’ broader investigations. On the other hand, in our era of hyper-partisan politics, even high-profile congressional investigations might not be as damaging to a president as they were in the past.

Republicans like Mueller a little less than they did when the report came out

When Mueller was appointed special counsel in May 2017, he was embraced on both sides of the political aisle as a trustworthy and impartial investigator. But that bipartisan warmth was fleeting. As the Russia investigation progressed, opinions about the special counsel became increasingly politically polarized, with more and more Republicans saying they distrusted Mueller, while his fan base among Democrats grew. That partisan acrimony mostly disappeared after the release of Barr’s summary, when support for Mueller rose among Republicans and fell among Democrats, but as the chart below shows, Mueller’s favorability among Republicans has dipped once again over the past few weeks, and he’s more popular again among Democrats.

Meanwhile, there’s still a seismic divide between Republicans and Democrats about what Mueller’s report concluded — specifically whether Trump obstructed justice by interfering with the special counsel’s investigation. According to a YouGov/The Economist poll conducted in late June, 83 percent of Democrats think Trump attempted to obstruct justice, compared to only 16 percent of Republicans. That gap has stayed basically consistent since the report was released, according to YouGov’s polling, which suggests that changing a significant number of minds about Trump’s behavior will be a tall order.

Of course, hearing the findings directly from Mueller could make a difference, since many Americans (and some members of Congress) admit they haven’t read the report. But while Democrats will be eager to draw out the parts of the report that look bad for the president, Republicans on both committees also will be ready to undermine Mueller’s credibility — which could just end up reinforcing the opinions that everyone already had.

Impeachment is popular among Democrats but nobody else

Some House Democrats are hoping Mueller’s testimony could help reinvigorate the push to start impeachment proceedings against the president. But that would require a big shift in public opinion. Right now, impeaching Trump still isn’t a broadly popular position. As the chart below shows, about half of Americans still oppose starting the impeachment process, and that really hasn’t changed much since the report was released.

Granted, the vast majority of Democratic voters do favor impeachment, but House Speaker Nancy Pelosi has been holding the line against impeachment proceedings for months now, so it’s not clear what would alter her calculus. Congressional Democrats are very divided on the topic — last week, the House blocked a proposal to impeach Trump with about 60 percent of Democrats on Pelosi’s side. Higher support for impeachment, particularly among Republicans or independents, could theoretically push more Democrats into the impeachment camp — but if Mueller’s testimony is bland or inconclusive, the necessary sea change in public opinion seems unlikely, particularly with the summer recess just days away.

It’s proving hard to weaken Trump with congressional investigations

This hearing is particularly high stakes for Democrats because so far, their investigations of the president and his administration haven’t made a dent in Trump’s approval rating. As I wrote earlier this year, political scientists have shown that sustained congressional investigations generally do have the power to weaken the president’s approval rating over time — making them a powerful weapon for the president’s opposing party.

But that was when presidents’ approval ratings tended to fluctuate over time and responded to events in the news. Opinions on Trump’s job performance, on the other hand, have been remarkably stable so far. (To be fair, so were Obama’s.) “It’s really hard to change people’s minds about Trump,” said Eric Schickler, a political science professor at the University of California Berkeley who studies congressional investigations. “So it’s very possible we’re in a new reality where congressional investigations just don’t do that much to weaken the president.”

This outlook seems bleak for the Democrats, but it’s possible that Mueller’s testimony could work in their favor, even if it doesn’t do much to shift views of Trump overall. They’ve faced across-the-board stonewalling from the Trump administration in response to requests for testimony and documents, so getting Mueller to testify at all was a rare bit of success because they’ve had very few splashy public hearings so far. If Mueller’s testimony does, in fact, turn out to be a “public spectacle” — as Attorney General Bill Barr has predicted — that could help refocus Democratic voters and the 2020 candidates on the report’s findings and potential misconduct by the president. After all, Mueller’s news conference in May, at which he spoke for less than 10 minutes and restated the report’s primary conclusions without taking questions, was enough to spark a new wave of calls for impeachment. Transforming the report into a true priority for voters could be harder, though — when a CNN poll in March asked respondents to name their top issue for 2020, none mentioned the Russia investigation.

There is another possible upside to Mueller’s testimony for Democrats, though — hearing from Muller could stop people from developing a more positive opinion about Trump. After all, his approval ratings remain low despite a strong economy, and they haven’t improved substantially since Mueller’s investigation ended. “We shouldn’t conclude that the Democrats are failing because they’re not having an impact on Trump’s approval rating,” Schickler said. “If their steady drumbeat of investigations and hearings can prevent Trump’s approval rating from increasing, that’s another kind of success.”