On August 7, 1974, three top Republican leaders in Congress paid a solemn visit to US President Richard Nixon at the White House, bearing the message that he faced near-certain impeachment because of eroding support in his own party on Capitol Hill. Nixon, who'd been entangled in the Watergate scandal for two years, announced his resignation the next day.
Could a similar drama unfold in later stages of the impeachment process that Democrats have now initiated against President Donald Trump?
It's doubtful. In Nixon's time, there were conservative Democrats and moderate Republicans. Compromise was not treated with scorn.
In today's highly polarised Washington, bipartisan agreement is a rarity. And Trump has taken over the Republican Party, accruing personal rather than party loyalty and casting the GOP establishment to an ineffectual sideline.
"In the past in the US, party members would dissociate themselves from disgraced leaders to preserve the party and their own reputations," said professor Nick Smith, who teaches ethics and political philosophy at the University of New Hampshire. "But now President Trump seems to have such a personal hold on the party — more like a cult leader than a US president — that the exits are closed as the party transforms into his image."
The delegation that visited Nixon was headed by Senator Barry Goldwater, of Arizona, the GOP's unsuccessful presidential candidate in 1964, Senator Hugh Scott, of Pennsylvania, and Representative John Rhodes, of Arizona — the leaders in their respective chambers.
They told Nixon there were no longer enough Republican votes to spare him from impeachment, given the release two days earlier of a 1972 tape recording contradicting Nixon's tenacious denial of any role in covering-up the Watergate break-in.
"He'd been proclaiming his innocence and suddenly they've got this evidence showing he's been lying all this time," said Thomas Schwartz, a history and political science professor at Vanderbilt University. "We don't have the equivalent of that now."
For now, Trump has a firewall in the form of Republicans who see more harm in opposing than supporting him.
Cal Jillson, a political science professor at Southern Methodist University, cited the increased political polarisation as a reason most Republican officials will stick with Trump.
"For the president's partisans in Congress, it's 'our guy on his worst day is better than your guy on his best day'.
"They stick with him to get the judicial appointments, the tax cuts."
That would change if Trump's troubles become so serious congressional leaders thought it would affect them and their party, Jillson said.
"Everyone among the Republicans in Congress has a beef with the president but they're afraid of him. If he weakens, that fear will subside."
The Watergate scandal overlapped the late stages of the Vietnam War, which had bedevilled Nixon and his Democratic predecessor, Lyndon Johnson.
In that era, Congress was more powerful in relation to the executive branch than now, with more leaders of national stature, experts said.
Kathleen Hall Jamieson, director of the University of Pennsylvania's Annenberg Public Policy Centre suggested after the death last year of Arizona Senator John McCain, there's no Republican in Congress who could replicate Goldwater's 1974 role.
"Who would go and be credible with Donald Trump, so that he would listen?" she asked. "Mitt Romney? Mitch McConnell? Lindsay Graham? Trump will turn on any of them the minute they say something uncongenial."
A key then-and-now difference, Jamieson said, is that Goldwater represented the same conservative constituency as Nixon and conveyed the message Nixon was losing its support. Whereas Trump's base is loyal to Trump personally.
One of the few Republicans in Congress to tangle regularly with Trump was Senator Jeff Flake, who decided not to seek reelection in 2018.
"The president's conduct in office should not surprise us. But truly devastating has been our tolerance of that conduct," Flake wrote in a Washington Post column.
David Gibbs, a political science professor at the University of Arizona, recalled Nixon had won reelection by a landslide in 1972, yet many who supported him, including Republicans in Congress, turned against him as evidence of a Watergate conspiracy accumulated.
In contrast, "the hyper-partisan tribalism makes bipartisan consensus for removing a president virtually impossible".
Another big change is the proliferation of media and advent of social media, used by Trump and partisans on all sides to promote their agendas and demonise opponents.