Democratic managers from the House of Representatives will try to convince both the Republican-controlled Senate, which will determine if Trump finishes his term, and the American public, which will decide in November if he gets a second one, that he improperly withheld key witnesses and documents.
In the third presidential impeachment trial in US history, Trump, a Republican, is accused of attempting to coerce Ukraine's government into digging up dirt on former Vice President Joe Biden, a top contender for the 2020 Democratic presidential nomination.
The US Constitution sets out the impeachment process for removing a president who commits "high crimes and misdemeanors." Trump has denied any wrongdoing, while Republican allies of the president have argued that his conduct does not rise to the level of an impeachable offense.
Once Democrats conclude their opening arguments, the president's legal team will have up to 24 hours over three days to mount a defense. Senate Republicans are expected to acquit Trump. A two-thirds vote of the chamber is required to eject him from office.
As the trial neared the end of its first week, there was little sign that Senate Republicans were being persuaded by the Democratic case.
Democrats spent Thursday meticulously detailing their allegations that Trump only grew interested in corruption in Ukraine when it appeared that Biden could become a serious political threat.
"If we allow this gross abuse of power to continue, this president would have free rein – free rein – to abuse his control of US foreign policy for personal interest, and so would any other future president," House manager Sylvia Garcia said late in Thursday's arguments. "And then this president, and all presidents, become above the law."
In a July 25 phone call, Trump pressed Ukrainian President Volodymyr Zelenskiy to investigate Biden and his son Hunter, who served on the board of Ukrainian energy company Burisma. Trump temporarily withheld $391 million in US military aid to Ukraine, which Democrats say was leverage for his demands.
In doing so, Trump abused the power of his office, Democrats say.
DEMOCRATS PUSH FOR WITNESSES
On Friday, they will argue that Trump also unlawfully refused to cooperate with the House probe of the matter by directing officials to ignore Democratic requests to testify and for relevant documents.
Key administration officials who refused to comply with subpoenas in the probe included Vice President Mike Pence, White House acting Chief of Staff Mick Mulvaney and Secretary of State Mike Pompeo. Former national security adviser John Bolton refused a request by the House to testify.
Democrats sought to have Bolton testify in the Senate proceeding, but senators voted along party lines on Tuesday against all Democrats' proposed witnesses.
In his opening remarks this week, Democratic Representative Adam Schiff, the lead House manager, accused Trump of using "unrivaled authority at his disposal as the commander in chief to cover up his wrongdoing."
White House Counsel Pat Cipollone, a member of Trump's legal team, called the obstruction charge "ridiculous" and contended the president had a constitutional right to keep aides from testifying.
Cipollone has called the process a "partisan impeachment" and accused Democrats of trying to "steal" the 2020 presidential election.
During the proceedings, Democrats have argued that the Senate should allow new witnesses such as Bolton to testify. Republicans have resisted their push but have threatened to call a witness such as Joe or Hunter Biden in retaliation.
The Senate could return next week to the question of whether to call witnesses.