President Donald Trump's defense team sparred with Democratic House managers in the Senate on Tuesday for the first time in the president's impeachment trial.
The battle on the Senate floor, presided over by Supreme Court Chief Justice John Roberts, largely centered around the rules that will be adopted for the trial proceedings going forward.
But the team of seven House Democrats, led by House Intelligence Committee Chairman Adam Schiff, D-Calif., also took the opportunity to lay out much of the evidence in their case that the president, for the first time in U.S. history, should be convicted and removed from office.
"When the Founders wrote the impeachment clause, they had precisely this type of conduct in mind," Schiff said in his opening statement. "Conduct that abuses the power of office for a personal benefit, that undermines our national security, and that invites foreign interference in the democratic process of an election. It is the trifecta of constitutional misconduct justifying impeachment."
Trump's lawyers argued in response that the president had done nothing wrong, and accused Democrats of ramming a biased investigation through to the Senate based on insufficient evidence.
"Never before in the history of our country has a President been confronted with this kind of impeachment proceeding in the House," said White House Counsel Pat Cipollone, who is leading the president's defense.
Trump was impeached by the House on Dec. 18 on articles of abuse of power and obstruction of Congress. Both articles relate to his efforts to pressure Ukraine President Volodymyr Zelenskiy into announcing probes involving his political opponent, former Vice President Joe Biden, and then blocking attempts from Congress to investigate.
It is considered highly unlikely that two thirds of the GOP-majority Senate, which was ordered to remain silent throughout the proceedings, will vote to remove a Republican president.
Here are the top moments of the day.
Some of the biggest fireworks of the day came hours before the trial proceedings kicked off.
On Monday evening, Senate Majority Leader Mitch McConnell, R-Ky., put forward an outline of the trial rules after suggesting he would aim to mimic the proceedings in former President Bill Clinton's 1998 impeachment trial.
But Democrats quickly cried foul on those rules, which departed from Clinton's trial in key sections — most notably in the time constraints placed on both sides to state their cases.
Senate Minority Leader Chuck Schumer, D-N.Y., called that resolution a "national disgrace" on Monday night. Before the proceedings began Tuesday afternoon, Schumer proposed a series of amendments to change the rules.
Before the House managers and defense team began their debate on the resolutions, McConnell said he would move to table — essentially, to ignore — amendments that would "force premature decisions on mid-trial questions."
Schumer tore into McConnell's proposed rules in a fiery speech. "This resolution," he said, will go down "as one of the darker moments in the Senate history. Perhaps one of even the darkest."
In its original form, McConnell's trial rules allotted 24 hours for House managers and Trump's defense team to state their case — but only allowed that time to be used over the span of two days for each side.
Schumer slammed those rules in his Senate floor speech.
"The McConnell resolution will result in a rushed trial with little evidence in the dark of night. Literally, the dark of night," he said. "If Leader McConnell is so confident the president did nothing wrong, why don't they want the case to be presented in broad daylight?"
But as the resolution on the trial rules was being read aloud in the Senate chamber, McConnell made two significant changes to his proposal.
The changes will permit each side to stretch out the 24 total hours they've been allotted for making arguments over three days, instead of two, as McConnell had initially proposed. The changes will also automatically admit into evidence the entire record of the House impeachment probe into Trump last fall.
"It's good they admitted evidence, but the real test will be witnesses and documents," Schumer told reporters after the rules were changed.
Schumer's office said McConnell was pressured to make the changes following massive pressure from Congress and the public. But McConnell may benefit from altering his own text.
By waiting as long as he did to announce the changes, McConnell ensured that his Democratic counterparts spent the day focused primarily on objecting to the specifics of those two rules. Less attention was paid to a third contentious issue in the trial rules: whether or not the Senate will hear from live witnesses.
McConnell has so far said that senators will be asked to vote on the witness question later in the trial, after they've heard arguments from each side. But Democrats say that amounts to voting on witnesses after the trial is essentially over.
Democrats wanted to subpoena the Trump administration for a slew of additional documents beyond what had already been gathered in the House impeachment inquiry.
They also want to subpoena witnesses, such as former national security advisor John Bolton and current acting White House chief of staff Mick Mulvaney, who did not testify in the House.
But a series of amendments put forward by Schumer were shot down along party lines in the Senate, where Republicans hold a 53-47 voting advantage.
As of 7:30 p.m. ET Tuesday, amendments were still being offered. Wednesday's proceedings were scheduled to begin at 1 p.m. ET.