After nearly three years, countless investigations, damning public testimonies and an explosive scandal to yet again rock Capitol Hill, the US House of Representatives has launched an impeachment inquiry against Donald Trump.

The probe focuses partly on whether the president abused his powers and sought help from a foreign government to undermine one of his 2020 rivals, Joe Biden, and help his own re-election. US House Speaker Nancy Pelosi said such actions would mark a “betrayal of his oath of office” and declared, “No one is above the law" when announcing the inquiry.

The inquiry sets up the party’s most direct and consequential confrontation with the president, injects deep uncertainty into the 2020 election campaign and tests anew the nation’s constitutional system of checks and balances.

Mr Trump, who thrives on combat, has all but dared Democrats to take this step, confident that the spectre of impeachment led by the opposition party will bolster rather than diminish his political support.

Meeting with world leaders at the United Nations, he previewed his defence in an all-caps tweet: “PRESIDENTIAL HARASSMENT!”

The Democrat challengers to Trump in 2020 Show all 25 1 /25 The Democrat challengers to Trump in 2020 The Democrat challengers to Trump in 2020 Bernie Sanders The Vermont senator has launched a second bid for president after losing out to Hilary Clinton in the 2016 Democratic primaries. He is running on a similar platform of democratic socialist reform Getty The Democrat challengers to Trump in 2020 Joe Biden The former vice president recently faced scrutiny for inappropriate touching of women, but was thought to deal with the criticism well and has since maintained a front runner status in national polling EPA The Democrat challengers to Trump in 2020 Elizabeth Warren The Massachusetts senator is a progressive Democrat, and a major supporter of regulating Wall Street Reuters The Democrat challengers to Trump in 2020 Amy Klobuchar Klobuchar is a Minnesota senator who earned praise for her contribution to the Brett Kavanaugh hearings Getty The Democrat challengers to Trump in 2020 Michael Bloomberg Michael Bloomberg, a late addition to the 2020 race, announced his candidacy after months of speculation in November. He has launched a massive ad-buying campaign and issued an apology for the controversial "stop and frisk" programme that adversely impacted minority communities in New York City when he was mayor Getty Images The Democrat challengers to Trump in 2020 Tulsi Gabbard The Hawaii congresswoman announced her candidacy in January, but has faced tough questions on her past comments on LGBT+ rights and her stance on Syrian President Bashar al-Assad Getty The Democrat challengers to Trump in 2020 DROPPED OUT: Pete Buttigieg The centrist Indiana mayor and war veteran would be the first openly LGBT+ president in American history Getty The Democrat challengers to Trump in 2020 DROPPED OUT: Deval Patrick The former Massachusetts governor launched a late 2020 candidacy and received very little reception. With just a few short months until the first voters flock to the polls, the former governor is running as a centrist and believes he can unite the party's various voting blocs AFP/Getty The Democrat challengers to Trump in 2020 DROPPED OUT: Beto O'Rourke The former Texas congressman formally launched his bid for the presidency in March. He ran on a progressive platform, stating that the US is driven by "gross differences in opportunity and outcome" AP The Democrat challengers to Trump in 2020 DROPPED OUT: Kamala Harris The former California attorney general was introduced to the national stage during Jeff Sessions’ testimony. She has endorsed Medicare-for-all and proposed a major tax-credit for the middle class AFP/Getty The Democrat challengers to Trump in 2020 DROPPED OUT: Bill De Blasio The New York mayor announced his bid on 16 May 2019. He emerged in 2013 as a leading voice in the left wing of his party but struggled to build a national profile and has suffered a number of political setbacks in his time as mayor AFP/Getty The Democrat challengers to Trump in 2020 DROPPED OUT: Steve Bullock The Montana governor announced his bid on 14 May. He stated "We need to defeat Donald Trump in 2020 and defeat the corrupt system that lets campaign money drown out the people's voice, so we can finally make good on the promise of a fair shot for everyone." He also highlighted the fact that he won the governor's seat in a red [Republican] state Reuters The Democrat challengers to Trump in 2020 DROPPED OUT: Cory Booker The New Jersey Senator has focused on restoring kindness and civility in American politics throughout his campaign, though he has failed to secure the same level of support and fundraising as several other senators running for the White House in 2020 Getty The Democrat challengers to Trump in 2020 DROPPED OUT: Wayne Messam Mayor of the city of Miramar in the Miami metropolitan area, Wayne Messam said he intended to run on a progressive platform against the "broken" federal government. He favours gun regulations and was a signatory to a letter from some 400 mayors condemning President Trump's withdrawal from the Paris Climate Accord Vice News The Democrat challengers to Trump in 2020 DROPPED OUT: Kirsten Gillibrand The New York Senator formally announced her presidential bid in January, saying that “healthcare should be a right, not a privilege” Getty The Democrat challengers to Trump in 2020 DROPPED OUT: John Delaney The Maryland congressman was the first to launch his bid for presidency, making the announcement in 2017 AP The Democrat challengers to Trump in 2020 DROPPED OUT: Andrew Yang The entrepreneur announced his presidential candidacy by pledging that he would introduce a universal basic income of $1,000 a month to every American over the age of 18 Getty The Democrat challengers to Trump in 2020 DROPPED OUT: Julian Castro The former San Antonio mayor announced his candidacy in January and said that his running has a “special meaning” for the Latino community in the US Getty The Democrat challengers to Trump in 2020 DROPPED OUT: Marianne Williamson The author and spiritual adviser has announced her intention to run for president. She had previously run for congress as an independent in 2014 but was unsuccessful Getty The Democrat challengers to Trump in 2020 DROPPED OUT: Eric Swalwell One of the younger candidates, Swalwell has served on multiple committees in the House of Representatives. He intended to make gun control central to his campaign but dropped out after his team said it was clear there was no path to victory Getty The Democrat challengers to Trump in 2020 DROPPED OUT: Seth Moulton A Massachusetts congressman, Moulton is a former US soldier who is best known for trying to stop Nancy Pelosi from becoming speaker of the house. He dropped out of the race after not polling well in key states Getty The Democrat challengers to Trump in 2020 DROPPED OUT: Jay Inslee Inslee has been governor of Washington since 2013. His bid was centred around climate change AFP/Getty The Democrat challengers to Trump in 2020 DROPPED OUT: John Hickenlooper The former governor of Colorado aimed to sell himself as an effective leader who was open to compromise, but failed to make a splash on the national stage Getty The Democrat challengers to Trump in 2020 DROPPED OUT: Tim Ryan Ohio representative Tim Ryan ran on a campaign that hinged on his working class roots, though his messaging did not appear to resonate with voters Getty The Democrat challengers to Trump in 2020 DROPPED OUT: Tom Steyer Democratic presidential hopeful billionaire and philanthropist Tom Steyer is a longtime Democratic donor AFP/Getty

So what comes next, and where does the country go from here? In order to make educated inferences, it's important to go back to the beginning of the scandal that got us here in the first place:

How did we get here?

The straw that seems to have broken the camel’s back was a phone call between Mr Trump and Ukrainian President Volodymyr Zelensky.

Mr Trump reportedly ordered his staff to freeze nearly $400m (£323.7m) in aid to Ukraine a few days before the phone call, in which he seemingly urged the Eastern European nation’s leader to investigate Mr Biden and his son, Hunter.

A memorandum the White House released on Wednesday from the call showed Mr Trump calling on Mr Zelensky to look into the matter, in which no evidence of wrongdoing on the part of the Bidens has been found.

“I will say that we do a lot for Ukraine,” Mr Trump said on the phone call, according to the memorandum. “We spend a lot of effort and a lot of time. Much more than the European countries are doing and they should be helping you more than they are. Germany does almost nothing for you. All they do is talk and I think it’s something that should really ask them about.”

He then asked Mr Zelensky to look into the Bidens, saying: “The other thing, there’s a lot of talk about Biden’s son, that Biden stopped the prosecution and a lot of people want to find out about that.”

“So whatever you can do with the Attorney General would be great,” he adds. “It sounds horrible to me.”

House speaker Pelosi announces Trump impeachment inquiry

The call sparked outcry across Washington before the White House released the memorandum, which was not, in fact, the fully “unredacted” transcript Mr Trump had claimed he authorised for release a day prior.

Ms Pelosi, after years of infighting within her party, finally caved to growing calls for impeachment when she announced the official inquiry on Tuesday afternoon.

Will the president actually be removed from office?

The burden will likely now shift to Democrats to make the case to a scandal-weary public. In a highly polarised Congress, an impeachment inquiry could simply showcase how clearly two sides can disagree when shown the same evidence rather than approach consensus.

Moreover, a two-thirds majority of the Senate would have to vote in favour of removing the president in order to have him ousted by an impeachment vote. So far, it does not appear likely the Republican majority will abandon Mr Trump.

Building towards this moment, the president has repeatedly been stonewalling requests for documents and witness interviews in the variety of ongoing investigations.

After Ms Pelosi’s announcement, the president and his campaign team quickly released a series of tweets attacking Democrats, including a video of presidential critics like the speaker and Democrat Ilhan Omar discussing impeachment. It concluded: “While Democrats ‘Sole Focus’ is fighting Trump, President Trump is fighting for you.”

Senate Majority Leader Mitch McConnell said Ms Pelosi’s well-known “efforts to restrain her far-left conference have finally crumbled.”

What needs to be done to get Republicans to join in on impeachment?

There are two possibilities for this to happen. The first depends on attitudes from Republican voters.

If Republican voters end up turning on Mr Trump, it is likely for the GOP—who are eager to keep their seats in Congress after their shackling in 2018—will follow suit.

The other possibility, according to some political theorists, is that Republicans could view Mr Trump’s impeachment as an opportunity to get the president they wanted all along: Vice President Mike Pence.

Can Mr Trump face jail time?

The Justice Department has taken the position that a sitting president cannot be indicted or prosecuted. But Mr Trump's fate could change if he is successfully impeached from office, or if prosecution begins after he serves his tenure in the White House.

California Congressman Adam Schiff, the Democratic chairman of the House Intelligence Committee, has said that Mr Trump “may be the first president in quite some time to face the real prospect of jail time”, saying it could be the case the Justice Department's decision to indict Mr Trump once he leaves office.

Prosecutors have argued that Mr Trump's former lawyer Michael Cohen “acted in coordination with and at the direction of” the president before his election to silence two women—Stormy Daniels and Karen McDougal—about their alleged affairs with the former reality TV star.

What would a Mike Pence administration look like?

There are stark differences in the way Mr Trump and Mr Pence handle political business. First, Mr Pence takes more of a traditionalist approach in communicating with the American people. Unlike Mr Trump, Americans probably won’t see Mr Pence tweeting out threats against world leaders or insults towards the press in the middle of the night.

When it comes to reproductive rights and women’s healthcare, Mr Pence is likely to vow overturning landmark Roe v. Wade and might champion the GOP agenda to defund Planned Parenthood. During his tenure as an Indiana congressional representative, Mr Pence made a name for himself through his stalwart commitment to reducing government spending. In 2003, Mr Pence fought “tooth and nail and led GOP caucus members” to prevent a prescription drug entitlement from being added to Medicare—proving that the vice president is willing to take on his own political party for limited government.

Essentially, Mr Pence is married to the concepts of limited government, deregulations, shrinking government and returning the powers to the states. His critics say one thing for certain: a Pence presidency could mean bad news for Medicare, women’s reproductive rights, civil rights, public education and climate change.

Can the president simply say, ‘You can’t fire me! I quit!

That's a possibility. Former President Richard Nixon took that route when he resigned from the Oval Office in August 1974. Historians believe that if Mr Nixon would have not resigned, he would have been impeached and removed from office.

Some legal experts believe Mr Trump could take a page out of Mr Nixon’s playbook. California Congresswoman Jackie Speier—a Democrat sitting on the House permanent select committee on intelligence—reportedly said that based on the growing evidence on the Trump campaign’s ties with Russia, she believes he might resign before impeachment.

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“I have always thought that he was never going to fulfil his full term,” Ms Speier said. “I am more convinced that he will leave before any impeachment would take place.”