When, with six American flags at her back, Nancy Pelosi stood in the hallway at the Capitol and, at 5pm on Tuesday, announced an official impeachment inquiry, it was the moment many Democrats had been waiting for.

It was also the moment many allies of Donald Trump had been waiting for.

As Democrats spent months on internal debates over whether to impeach the president, Republicans and conservative media were ready to march in lockstep and mobilise a strategy to weaponise impeachment for their own electoral advantage.

Following Pelosi’s announcement, they launched an offensive on multiple fronts to discredit her, throw fresh dirt at Joe Biden and paint the Ukraine affair as a Russia hoax redux designed to overturn the 2016 election – and raise cash via a swiftly launched “Official Impeachment Defense Task Force”.

Far from the consensus that eventually led to the downfall of Richard Nixon, the whiff of impeachment merely inflamed a sense of divisiveness, alternative realities and an ugly political brawl that could make last year’s clash over the nomination of Brett Kavanaugh to the supreme court look positively tame.

Impeachment plays into Trump’s performance of victimhood and grievance against the political establishment. Accused of inviting a foreign government to interfere in American democracy, he tweeted about “a total witch-hunt scam by the Democrats” and claimed “presidential harassment”.

Stephanie Grisham, the White House press secretary, followed up with a statement that Democrats’ “attacks on the president and his agenda are not only partisan and pathetic, they are in dereliction of their constitutional duty”.

Play Video 1:01 'It's a witch-hunt': Donald Trump lashes out as impeachment calls grow – video

At the sound of the klaxon, Trump’s troops ran to their battle stations. His son Donald Trump Jr and lawyer Rudy Giuliani used a favourite tactic of accusing the accusers, recycling baseless allegations against Biden.

Don Jr tweeted: “Amazing that Biden gets the pass on using his office to enrich his son, but the mere chance to somehow make it about @realDonaldTrump is all the Dems need to go all out. JOKERS!”

Giuliani added: “Dems have no basis for impeachment. They should be investigated for obstructing justice. Their whistleblower may turn out to have no direct evidence. The story is so far off it sounds like another Dem-Media frame-up. Only crimes are Biden-Kerry pay-for-play. Thank you.”

No evidence has emerged to support Trump’s claims that Biden improperly used his position as vice-president to push out a Ukrainian prosecutor in order to help his son.

Republicans shrugged off the central allegation that Trump pressured the leader of Ukraine to investigate Biden’s son after withholding military aid. They made clear that, even if Trump is impeached by the House of Representatives, they have no intention of convicting him in the Senate and removing him from office.

Q&A How do you impeach the US president? Show Hide Article 1 of the United States constitution gives the House of Representatives the sole power to initiate impeachment and the Senate the sole power to try impeachments of the president. A president can be impeached if they are judged to have committed "treason, bribery, or other high crimes and misdemeanors" – although the US Constitution does not specify what “high crimes and misdemeanors” are.

The formal process starts with the House of Representatives passing articles of impeachment, the equivalent of congressional charges. According to arcane Senate rules, after the House notifies the Senate that impeachment managers have been selected, the secretary of the Senate, Julie Adams, tells the House that the Senate is ready to receive the articles. Then impeachment managers appear before the Senate to “exhibit” the articles, and the Senate confirms it will consider the case. The presiding officer of the Senate notifies the supreme court chief justice, John Roberts, of the impending trial. Roberts arrives in the Senate to administer an oath to members. The presiding officer will then administer this oath to senators: “I solemnly swear that in all things appertaining to the trial of the impeachment of Donald Trump, now pending, I will do impartial justice according to the constitution and laws, so help me God.” The Senate must vote on a resolution laying out ground rules for the trial including who the key players will be, how long they will get to present their cases and other matters. After the Senate is “organized”, the rules decree, “a writ of summons shall issue to the person impeached, reciting said articles, and notifying him to appear before the Senate upon a day and at a place to be fixed by the Senate”. A president has never appeared at his own impeachment trial. Trump will be represented by the White House counsel, Pat Cipollone, and his personal lawyer Jay Sekulow, among others. After the oath, the trial proper will begin. Senators may not speak during the proceedings but may submit written questions. The question of witnesses and other matters would be decided on the fly by majority vote. A time limit for the proceedings will be established in the initial Senate vote. The senators will then deliberate on the case. In the past this has happened behind closed doors and out of public view. The senators vote separately on the two articles of impeachment – the first charging Trump with abuse of power, the second charging him with obstruction of Congress. A two-thirds majority of present senators – 67 ayes if everyone votes – on either article would be enough to convict Trump and remove him from office. But that would require about 20 Republicans defections and is unlikely. The more likely outcome is a Trump acquittal, at which point the process is concluded. Two presidents have previously been impeached, Bill Clinton in 1998, and Andrew Johnson in 1868, though neither was removed from office as a result. Richard Nixon resigned in 1974 before there was a formal vote to impeach him. Tom McCarthy in New York

The Senate majority leader, Mitch McConnell, accused Democrats of a rush to judgment. “It simply confirms that House Democrats’ priority is not making life better for the American people but their nearly three-year-old fixation on impeachment,” he said.

A slew of other Republicans issued statements joining the condemnation. Liz Cheney, chair of the House Republican conference and daughter of the former vice-president Dick Cheney, accused Pelosi of jumping the gun without firm evidence. “She has announced a formal impeachment inquiry of the President of the United States based on news reports of a phone call and a whistleblower,” Cheney said of the speaker.

“The Speaker and House Democrats have lost all credibility and, most tragically, have abdicated their duty to the Constitution and to the American people.”

The Republican National Committee was also circling the wagons. Steve Guest, its rapid response director, wrote in an email: “The Democrat-led impeachment inquiry is not based on facts, it solely stems from their political vendetta against President Trump.

“Reminder: Democrats already tried once with a failed Russia hoax and as we all know: No Collusion. No Obstruction. So now they cooked up a ridiculous Ukraine hoax even before they have read the transcript of the call.”

Meanwhile the Trump-Pence campaign for 2020 sent out fundraising emails. One began: “Nancy Pelosi just formally called for the first step towards my impeachment! This is just another smear job and pathetic attempt by Democrats to rip the power from the people. I’ve done nothing wrong. Trust me, you’ll see the transcript.”

It announced the launch of the “Official Impeachment Defense Task Force” and sought donations.

Play Video 1:17 Nancy Pelosi accuses Trump of 'betrayal' as she announces impeachment inquiry – video

Some Democrats have long feared that impeachment could backfire by rallying Trump’s base and deepening a sentiment of “us versus them”. Trump’s backers certainly hope so. Brad Parscale, his 2020 campaign manager, said: “Democrats can’t beat President Trump on his policies or his stellar record of accomplishment, so they’re trying to turn a Joe Biden scandal into a Trump problem.”

On Tuesday night, Tucker Carlson, a host on Rupert Murdoch’s Fox News network, played dazed and confused, saying he had been trying all day to understand what Democrats were alleging. “Even allowing for the hysteria of the moment,” he said, “this seems pretty reckless.”

An hour later, his fellow host Sean Hannity, who is friendly with Trump, was predictably incensed. “The psychotic anti-Trump hysteria, it has now completely overtaken the entire Democratic party,” he told viewers. “What is happening is dangerous to this country. It is grossly political, will forever alter how any president in the future in his constitutional role as commander-in-chief will be able to communicate freely with other world leaders.”

An entire rightwing ecosystem had kicked in, demonstrating how difficult it will be for the impeachment case to penetrate the Trump universe. Kurt Bardella, the president of the strategic communications firm Endeavor Strategies and a former congressional aide, said the entire Trump presidency had proved “nothing will deter the majority of Republicans and their propaganda platforms from standing by their man.

“Trump’s support of a serial sexual predator like Roy Moore didn’t do it. Trump’s refusal to acknowledge Russia’s efforts to undermine our democracy didn’t do it. Trump’s relentless campaign to profit from his presidency didn’t do it. Trump’s blatant displays of racism didn’t do it. Certainly the president’s plot to hold foreign aid hostage in order to extort an investigation into a political rival won’t change the equation for the GOP.”