Starting Wednesday, Americans will have the opportunity to see for themselves what's been happening behind closed doors on Capitol Hill. The question is whether the House Intelligence Committee's public hearings will change public opinion on impeachment — or lock it into place.

Currently, support for impeaching and removing President Donald Trump stands at about 49 percent in a running average of polls. Opposition is at 46 percent. Notably, these numbers are almost exactly in line with the 2016 election result, when Trump received 46 percent of the national popular vote to Hillary Clinton's 48 percent. The partisan divide is stark: Ninety-one percent of Democrats back removing Trump from office in the latest NBC News/Wall Street Journal poll, compared with only 6 percent of Republicans.

In other words, public opinion on impeachment now resembles the basic political divide that has defined the Trump era.

This is why, as of now, it is likely that Trump will be impeached in the House and acquitted by the Senate. It would take significant defections from either party — Democratic lawmakers defying the overwhelming consensus of Democratic voters or Republican lawmakers bucking equally strong opinion among Republican voters — to produce any other outcome.

The hope among Democrats is that the hearings will feature televised testimony so compelling that public opinion breaks decisively toward impeachment, thereby scrambling the politics on Capitol Hill. For encouragement, they often invoke a past impeachment inquiry in which public hearings did play a crucial role.

In the Watergate saga, there were two sets of public hearings, and each built support for President Richard Nixon's impeachment.

The first were the Senate Watergate hearings, held in the summer and fall of 1973 to investigate the Watergate break-in and its connections to Nixon's re-election effort the year before. The hearings, which featured dramatic testimony and exchanges ("What did the president know and when did he know it?"), raised public awareness of the Watergate matter and convinced a majority of Americans that Nixon had either had foreknowledge of the break-in or had tried to cover it up after the fact.

The other major public hearings came in July 1974, when the House Judiciary Committee drew up and debated five articles of impeachment against the president, ultimately adopting three of them. A Harris poll at the time found that the Judiciary hearings increased support for impeaching Nixon to 66 percent from 53 percent. Critically, the same poll found Nixon's Republican base divided, with 44 percent backing impeachment and 45 percent opposing it. Days later, following the release of the "smoking gun" tape, Nixon resigned from office.

As tantalizing as the comparison is for Democrats, there's reason to doubt that the coming Ukraine hearings will lead to a similar shift in public opinion.

The media landscape of the mid-'70s was far narrower than today's. There was no internet or social media. Cable television was barely a rumor. Most Americans relied on the broadcast networks, their daily newspaper and perhaps the radio for news. Their exposure to competing narratives was limited. With major outlets largely telling the same story, public opinion moved with each new development.

A more apt comparison for the politics of the present might be found in the impeachment of President Bill Clinton.

Opposition to impeaching Clinton was strong from beginning to end, but Republicans still convened Judiciary Committee hearings in November 1998. They produced no significant revelations — everyone already knew that Clinton had engaged in an affair with a former White House intern and lied about it — and succeeded only in rallying the GOP base more squarely behind impeachment. In a near-party line vote, the House ultimately impeached Clinton, who was then acquitted in the Senate.

In the two decades since, the country has grown only more polarized.

The facts are far different now, but as in Clinton's case, they are already widely known, absent a new disclosure. But for all of the revelations about the Trump White House's dealings with Ukraine, there's scant evidence so far that Republican voters are rethinking their opposition to impeachment. And as long as Republican voters remains squarely behind him, it's hard to see Trump suffering more than a handful of defections from Republican lawmakers.