Jurors at US Senate will decide if President Trump abused his office and obstructed Congress as charged in two articles of impeachment approved last month by the House of Representatives.
The historic impeachment trial of US President Donald Trump opened the debate with fireworks on Tuesday as Democrats accused Senate Majority Leader Mitch McConnell of fomenting a "cover-up" with his proposed rules for the process.
The Republican McConnell proposed a set of ground rules that would place strict restrictions on witnesses and evidence for the first stage and move the trial quickly ahead, saying he would summarily block any Democratic attempts to change his rules.
"The basic structure we're proposing is just as eminently fair and even-handed," McConnell.
"There is no reason why the vote on this resolution ought to be remotely partisan," he said.
A 'rigged' trial
McConnell is organising a "rigged" impeachment trial for President Trump and working "in concert" with the president, chief House prosecutor Adam Schiff said on Tuesday.
"This is a process for a rigged trial," Schiff, the Democratic chairman of the House Intelligence Committee, told reporters after McConnell released proposed rules for the historic Senate trial.
"This is the process if you do not want the American people to see the evidence," said Schiff, who led the investigation that resulted in Trump's December 18 impeachment by the House of Representatives.
"This is a process you use if you want to, hand in hand, working in concert with the president, allow the president to continue to obstruct the Congress and deny the truth to the American people," Schiff said shortly before the Senate was to debate the rules.
Third impeachment trial
Four months after the Ukraine scandal exploded and went on to overshadow the end of Trump's term, and 10 months before Americans go to the polls to decide whether to re-elect him, the 100 members of the Senate gathered at 1800GMT, with chief justice John Roberts presiding over the trial.
The job of these lawmakers, sworn in last week as jurors, is to decide if Trump abused his office and obstructed Congress as charged in two articles of impeachment approved last month by the House of Representatives.
They state that Trump tried to pressure Ukraine into interfering in the 2020 US election to help him win, and then tried to thwart a congressional probe of his behaviour.
It will be only the third time a president has endured an impeachment trial, after Andrew Johnson in 1868 and Bill Clinton in 1999.
Part of the scandal centres on a July 25 telephone call in which Trump pressured Ukrainian President Volodymyr Zelensky to announce an investigation of former Vice President Joe Biden, Trump's potential opponent in the November vote.
Democrats, who control the House of Representatives and led the investigation, accuse Trump of manipulating Ukraine by withholding nearly $400 million in military aid for its war against Russian-backed separatists and a White House meeting for Zelensky until the latter announced a Biden probe.
"The president did nothing wrong," Trump's lawyers responded in a 110-page brief submitted to the Senate on Monday.
This echoes the repeated assertions of the 73-year-old real estate magnate that the saga is a political witch hunt and a hoax, and that his phone call with the Ukrainian leader was "perfect".
In the president's brief, his 12-man legal team contested the very idea of his impeachment.
They called the two articles of impeachment – approved largely along party lines in the Democratic-controlled House – the product of "a rigged process" and "constitutionally deficient on their face" because they involved no violation of established law.
That team, which has recruited high profile lawyers such as Kenneth Starr, who tried to bring down Clinton over his affair with Monica Lewinsky, said in the brief: "the Senate should reject the Articles of Impeachment and acquit the president immediately."
"President Trump abused the power of his office to solicit foreign interference in our elections for his own personal political gain, thereby jeopardizing our national security, the integrity of our elections, and our democracy," the House managers said Saturday in a memorandum.
They said the president's behaviour "is the Framers' worst nightmare", referring to the authors of the US Constitution, and that Trump deserves to be removed from office.
But Trump looks almost certain to be acquitted because of the 53-47 Republican majority in the Senate.
Trump was abroad as proceedings against him opened; Trump left late Monday for the economic forum in Davos, Switzerland.
How long the trial will last is up in the air.
Senate Democratic leader Chuck Schumer said McConnell is rushing the trial and also making it harder for witnesses and documents to be presented.
"On something as important as impeachment, Senator McConnell's resolution is nothing short of a national disgrace," Schumer said in a statement.
The Democrats want key Trump administration officials to testify, such as acting chief of staff Mick Mulvaney and former national security adviser John Bolton, in the belief that they know a lot about Trump's dealings with Ukraine. Bolton has said he is willing to testify if subpoenaed.
The White House has said it expects the trial to be over in two weeks. Clinton's trial lasted five weeks.