Here’s what you need to know:
The Senate’s historic trial of President Trump begins in earnest with a bitter fight.
The Senate convened shortly after 1 p.m. on Tuesday to start in earnest the impeachment trial of Mr. Trump, who faces charges that he abused the power of his office and obstructed Congress. Senators were warned that they had to remain quiet, a skill that they rarely exercise in the Senate chamber, or face imprisonment.
The first order of business was a debate over the format of the trial, a draft of which Senator Mitch McConnell, Republican of Kentucky and the majority leader, released on Monday. Democrats spent the morning lashing out against Mr. McConnell’s plan, accusing him and other Republicans of trying to cover up Mr. Trump’s actions.
Unlike most other debates in the Senate, the elected senators will not be doing the debating. Instead, the seven House impeachment managers, who are serving as prosecutors in the case, and Mr. Trump’s legal defense team will argue over the rules that will govern the proceedings. The first round of the debate on Tuesday is expected to last two hours.
In a last-minute change to Mr. McConnell’s proposal, each side will have three days, not two, to present their cases.
The House impeachment managers and Mr. Trump’s defense team will each have an additional day to argue their cases under the proposed rules the Senate began considering Tuesday afternoon.
This is a change from Mr. McConnell’s initial proposal, which gave each side up to 24 hours over two days — a time frame Democrats criticized because it could push key testimony into early morning hours, when most Americans would be sleeping.
Each side still gets a total of 24 hours to present, but spreading it across three days will give both legal teams more time to lay out their cases and end the days earlier.
Mr. McConnell made the change after key Republican senators, including Susan Collins of Maine, argued that the rules for Mr. Trump’s impeachment trial should not deviate from the rules used during the only modern precedent, the impeachment trial of President Bill Clinton in 1999.
Ms. Collins, a moderate Republican who is likely to face a tough re-election bid later this year, has significant sway with Mr. McConnell, as her votes could change the outcome of the trial.
Democrats are appalled by Mr. McConnell’s plan for the trial.
For weeks, Mr. McConnell, who has significant control over how the trial unfolds, has said Mr. Trump’s trial would be modeled after the Senate’s structure for Mr. Clinton’s trial.
But the proposal Mr. McConnell released Monday evening had some significant differences, including a provision that would speed up the time allowed for opening arguments. It would also allow admitting the records generated by the House impeachment inquiry into evidence only if a majority of senators agree to doing so. In the Clinton trial, those records were admitted automatically. Mr. McConnell appeared to walk back that change Tuesday. The rules he submitted to the Senate would automatically enter the evidence collected by the House impeachment inquiry into the Senate record of the trial.
Representative Adam B. Schiff, Democrat of New York and one of seven House impeachment managers who will argue for impeaching President Trump during the Senate trial, said Tuesday that a key element of the rules for Mr. Clinton’s trial was that they were agreed on by the Senate’s top Republican and Democrat.
Mr. McConnell’s Democratic counterpart, Mr. Schumer of New York, was not consulted.
Democrats have also pushed for the trial rules to allow for calling witnesses and admitting new documents into evidence. Mr. McConnell’s plan would have the Senate first vote on whether they want to consider new evidence at all. If a majority of senators agreed to do so, then they would vote on admitting specific witnesses or documents individually.
Mr. Schiff said what Mr. McConnell had offered did “not describe the process for a fair trial.”
Mr. Schumer said the first amendment he planned to offer to Mr. McConnell’s rules would require the Senate to subpoena White House documents related to the charges against Mr. Trump.
As his trial progresses, Mr. Trump is boasting about the American economy in Switzerland.
While the Senate trial commenced with hours of debate over the format of Mr. Trump’s trial, the president met with world leaders at the annual World Economic Forum in Davos, Switzerland, where he trumpeted the strong American economy, heaping praise upon himself.
But when Democrats called for the White House counsel, Pat A. Cipollone, to turn over documents related to the Ukraine matter, the White House hit back with a sharp statement on Mr. Trump’s behalf.
“The Democrats are an utter joke — they have no case, and this latest political stunt proves it,” said Hogan Gidley, a White House spokesman. “The idea that the counsel to the president has to turn over protected documents and confidential information is ludicrous, and to imply he can’t represent the president of the United States in an impeachment proceeding is completely absurd.”
Earlier on Tuesday, when Mr. Trump was asked a question about the impeachment trial, taking place thousands of miles away, he said, “That whole thing is a hoax.”
President Volodymyr Zelensky of Ukraine, whose call with Mr. Trump led to the whistle-blower complaint that jump-started the impeachment inquiry, is also at the Davos forum. It was unclear if the two world leaders would meet at some point.
While impeachment loomed large over Mr. Trump and his aides, the president’s economic policies drew a favorable response among the wealthy audience at Davos, many of whom were wary of what a progressive Democrat taking over the Oval Office could mean for them.