Doug Collins, top Republican on the judiciary committee, said the effort was a continuation of three years of efforts by his counterparts to remove Trump from office.

«Today’s going to be a lot of things. What it is not is fair. What it is not is about the truth,» said Collins.

6 hours of debate on tap

Democrats overwhelmingly approved the rules for the debate, 228-197, with just two defections from Pelosi’s ranks. Democrats did pick up backing from Justin Amash, the Michigan conservative who left the Republican Party this year to become an Independent over his support for impeachment.

The legislators will now debate the two articles throughout the day. The House’s rules committee set aside six hours for the debate, over the objection of the panel’s Republicans, who pushed for 12 hours.

Earlier, Republicans launched several procedural efforts, including trying to force a vote condemning the actions of Democratic committee leaders, based on objections to the way the hearings were conducted. The motions were voted down in the Democratic-led House.

Trump, who would become just the third U.S. president to be impeached, on Tuesday fired off a furious letter to Pelosi denouncing the «vicious crusade» against him, but he also acknowledged he was powerless to stop the expected outcome.

He conveyed his disgust in a series of tweets on Wednesday, urging his followers to «say a PRAYER!»

The president has implored Americans to «read the transcript,» but the facts of his July phone call with the Ukraine president were largely confirmed by witnesses in the impeachment inquiry. Trump asked Volodymyr Zelensky to investigate Democrats and his 2020 political rival Joe Biden.

At the time, the newly elected Ukraine leader was hoping for a coveted White House visit to showcase his standing with the U.S., his country’s most important ally. He was also counting on nearly $400 million in military aid as his country confronts a hostile neighbour, Russia.

The two leaders have never met at the White House — though they did so on the sidelines of the UN meeting in September — and the aid was delayed for three months, around the time the impeachment inquiry ramped up.

The question for lawmakers is whether those actions, and the White House’s block on officials testifying before the House investigation, are impeachable offences.

«This is a democracy-defining moment. History will judge us by whether we keep intact that fragile republic handed down to us by our forebears over 200 years ago — or whether we allow it to be changed forever,» said Jim McGovern of Massachusetts, Democratic chair of the House’s rules committees.

Oklahoma’s Tom Cole, that committee’s top Republican, countered, «Today after a truncated investigation that denied the president due process … Democrats in the House are pressing forward with a partisan impeachment vote.»

As the historic event played out in Washington, tens of thousands of Americans were set to rally at various locations across the country, some of which began on Tuesday evening.

Articles of impeachment

Article 1

In the impeachment context, abuse of power is generally defined as using the vast powers of the presidency for personal benefit.

Abuse of power is not specifically listed as an impeachable offence in the U.S. Constitution, which states that a president can be removed from office for «treason, bribery, or other high crimes and misdemeanours.»

But the founders of the United States intended the phrase «other high crimes and misdemeanours» to broadly encompass abuses of power, legal scholars said.

Article 2

Democrats levelled the obstruction charge based on Trump’s stonewalling of the House’s impeachment inquiry. The White House has refused to provide documents to congressional investigators and has instructed top advisers and government officials to defy subpoenas and refuse to testify.

Contempt of Congress is a misdemeanour crime under U.S. law, which defines the offence as wilfully failing to provide testimony or documents to Congress.

What to expect

If the impeachment is approved, the House would select lawmakers known as managers to present the case against Trump at a Senate trial. House Democrats say most of the managers are likely to come from the judiciary committee, and possibly from the intelligence committee that led the investigation.

Trump would remain in office pending a trial in the Senate. A two-thirds majority of those present in the 100-member Senate would be needed to convict Trump, which is unlikely.

U.S. Chief Justice John Roberts would preside over the trial. House managers would be chosen to present their case against Trump, and the president’s legal team would respond.

Senators hear the evidence, but are not to interrupt the proceedings. In the last impeachment trial involving a president, which lasted 37 days, they deliberated in private before voting.