On August 7, 1974, a trio of top Republican leaders went to the White House and told President Richard Nixon that party support was eroding and impeachment was inevitable.

He resigned the next day.

Fast forward 45 years, and another US president, Donald Trump, is facing impeachment by the House of Representatives and a potential trial in the Senate.

Unlike Nixon, however, Trump appears to enjoy - at least for the time being - the support of Republican lawmakers, and has given no hint that he'll buckle in the face of what he calls a partisan "witch hunt."

"Part of the story of Watergate and the investigation is watching Republicans peel off, start to call into question their support for Nixon," said Kevin Mattson, a professor of contemporary history at Ohio University.

"Now they just seem to be stiffening," said Mattson, author of "Rebels All!: A Short History of the Conservative Mind in Postwar America."

"Partisanship is so much stronger today than it was back in the days of Watergate."

Trump is accused of withholding vital military aid from Ukraine, a country at war with Russia, in a bid to elicit political dirt on potential 2020 Democratic rival Joe Biden.

Adam Schiff, chairman of the Democratic-controlled House committee conducting the impeachment inquiry, claimed that Trump's conduct goes "beyond anything Nixon did."

"What we've seen here is far more serious than a third-rate burglary of the Democratic headquarters," Schiff said in a reference to the 1972 break-in at the Watergate hotel that led to a cover-up attempt and eventually Nixon's resignation.

Trump, like Nixon, is accused of "using the powers of the presidency for personal political reasons," said Jon Marshall, an assistant professor at Northwestern University's Medill School of Journalism.

But the accusations against Trump are indeed more serious than those facing Nixon, said Louis Caldera, who served as Secretary of the Army under president Bill Clinton and now teaches at American University.

"One is just about domestic politics," Caldera said, while Trump "withheld military aid to an ally at war."

"He's not advancing legitimate US national or foreign policy ends," he said. "He's basically trying to stir the pot to create problems for a political rival."

Alan Baron, a lawyer who served as special impeachment counsel in the cases of four federal judges, said Trump's actions were essentially a shakedown that "makes Watergate look like child's play."

What's changed since Nixon faced impeachment and today, Marshall said, is the "media environment and the nature of our politics.

"There was much more bipartisanship in the 1970s in Congress than there is now," said Marshall, author of "Watergate's Legacy and the Press: The Investigative Impulse."

"There were conservative Democrats and there were liberal Republicans and they were used to working together."

As for the media landscape, "the status of the media and how much people trust the media is just radically different now than it was in the 1970s," said Mattson.

The three network TV channels in the 1970s and a few major newspapers and news magazines "really determined the coverage," Marshall said.

"It's much easier now for people to choose a partisan outlet that they feel comfortable with," he said. "And of course we now have an infinite number of social media outlets and websites that people can go to get their own partisan spin on things."

In addition, Marshall said, Trump can take his case to the American people directly through Twitter while Nixon only had recourse to occasional news conferences.

With Trump capable of firing off an angry tweet at any moment, "members of Congress cross this president at their peril," Caldera said, knowing opposition could endanger their chances of re-election.

To make their case for impeachment, Democrats have held five days of public hearings featuring 12 witnesses but the White House has refused so far to turn over documents or allow top Trump aides to testify.

"Eventually during Watergate, the White House tapes were produced and that was the smoking gun that was aimed directly at the president - you could hear his voice ordering a cover-up," Marshall said. "And in the end, all of Nixon's top aides testified."

At the end of the day, Caldera said, Democrats - with or without a smoking gun - are going to have to "convince the American people that what was done (by Trump) was an abuse of power."

"If there's public support for impeachment, than that creates the cover for Republican members to be courageous," he said. "Without that, they're not going to be courageous."

Copyright Agence France-Presse, 2019