The United States is on the cusp of a historic moment: Donald Trump is about to become the third President ever impeached.

It's the sort of event that used to stop the nation and be treated with the upmost solemnity.

Which US presidents have been impeached? President Andrew Johnson was impeached in 1868 for appointing a cabinet member without Senate approval

President Andrew Johnson was impeached in 1868 for appointing a cabinet member without Senate approval Articles of impeachment were drawn up for Richard Nixon in 1974, but he then resigned

Articles of impeachment were drawn up for Richard Nixon in 1974, but he then resigned Bill Clinton was impeached in 1998 over his affair with Monica Lewinsky

Bill Clinton was impeached in 1998 over his affair with Monica Lewinsky No US president has ever been convicted of an impeachable offence

Impeachment lives forever in books and biographies — a permanent blot on any leader's legacy.

Many Americans of a certain age will tell you they remember what they were doing the moment Bill Clinton faced the same fate, or how they gathered around TV sets to watch Richard Nixon resign in order to avoid the humiliation.

But in today's hyper-partisan world, things are different.

Views on these impeachment proceedings are baked in, the outcome looks a foregone conclusion and it feels a little like the nation is just going through the motions.

Impeachment — like much in Trump's America — has lost some of its seriousness.

The commander-in-chief doesn't even seem to fear it.

Democrats have kept their case simple

The President's Democratic opponents are aware of this.

For a long time, they've known they were going to impeach Mr Trump, the only real question was: for what?

Democrats including Nancy Pelosi announced two articles of impeachment against Donald Trump. ( Reuters: Yuri Gripas )

Despite speculation they would deliver a long list of offenses, they've drawn up just two articles.

The first alleges the President used his office to pressure Ukraine for political gain by turning military aid and a White House visit into bargaining chips.

Democrats claim Mr Trump wanted politically beneficial investigations in return, including one that would have ensnared his leading opponent, Joe Biden.

There are gaps in the case, partly because the White House has withheld documents and stopped members of the administration from cooperating with the impeachment inquiry.

Donald Trump's impeachment proceedings centre around a phone call to Ukraine's leader Volodymyr Zelenskiy. ( Reuters: Jonathan Ernst )

Democrats say that move was a deliberate attempt to kill their investigation, so they have brought a second charge — obstruction of Congress.

They ignored the temptation to accuse President Trump of bribery or wrap in all the extra evidence from the Mueller report.

It's a narrow case and simple narrative.

Democrats say the President abused his power to get help from a foreign country ahead of next year's election and then tried to cover it up.

They're betting it's a story an increasingly divided and fed-up nation can understand.

American voters' views on impeachment seem set

Because as things stand, there's almost no chance Mr Trump will actually be removed from office in a Senate trial.

Next year, the success or failure of this impeachment push is going to be measured in the court of public opinion.

A recent survey showed voters from three crucial swing states — Michigan, Pennsylvania and Wisconsin — are currently opposed.

Meanwhile, an analysis by website FiveThirtyEight, highlights how split the country is on the issue — 47.9 per cent of Americans are in favour of impeachment and 43.6 per cent are against it.

Only a substantial, sudden shift in those numbers would convince Mr Trump's Republican colleagues, who control the upper house of Congress, to turn against him.

Republicans continue their war on impeachment process

For the most part, they haven't bothered to dispute the evidence.

Donald Trump lashed out at Democrats, calling the impeachment process against him a "witch hunt." ( AP: Manuel Balce Ceneta )

Instead, they either dismiss the case outright or claim there aren't enough damning details to warrant impeaching a President.

A key part of their defence strategy has been to attack the entire process and turn it into as much of a raucous, partisan brawl as possible — an extension of a cable TV slanging match.

They've got their lead from Mr Trump, who has been trying to use his impending impeachment as a rallying cry and fundraising tool at events across the United States.

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The White House's attention has firmly turned to managing the optics of the Senate trial.

Mr Trump claims he wants a chance to mount a defence and call several witnesses, perhaps even Mr Biden.

Trump's strategy is to get it over with

At least one his allies, however, thinks that would be a mistake.

"If the Senate is ready to vote and ready to acquit you, you should celebrate that," Republican Senator Lindsey Graham urged the President on Sunday.

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He wants impeachment all over and done with as quickly as possible. Right now, it seems like that could be the best strategy.

It's worth remembering that a year ago, Mr Trump was about to write another divisive chapter in the nation's history by triggering the longest government shutdown on record.

The cause, for those who have already forgotten, was a funding fight over his much-promised border wall.

It was a significant moment — many commentators muttered about potential electoral consequences.

Now, it's a speck in the rear vision mirror.

Of course, the impeachment of a president is a rarer and more consequential event.

But in these chaotic, political times it's not hard to imagine that even impeachment might be eclipsed by the time voters head to the ballot boxes in November next year.