The U.S. Senate formally received President Donald Trump’s impeachment articles on Thursday, and Chief Justice John Roberts swore in the men and women who will determine if the nation’s duly elected chief executive should be removed from office.

Opening arguments in President Trump’s impeachment trial will begin at 1 p.m. on Jan. 21.

Roberts was escorted into the Senate chambers at 2 p.m. by U.S. Sens. Roy Blunt (R-Mo.), Patrick Leahy (D-Vt.), Lindsay Graham (R-S.C.) and Dianne Feinstein (D-Calif.) U.S. Rep. Adam Schiff (D-Calif.), who is lead prosecutor in the case, formally presented the articles to the Senate at 10 a.m.

The U.S. Constitution calls for the Supreme Court’s chief justice to preside at the trial, administer the oath to senators who will serve as jurors and swear to deliver “impartial justice.”

»Meet the man presiding over Trump’s impeachment trial

After weeks of delay, the U.S. House officially transmitted two articles of impeachment against the president to the Senate on Wednesday. Senate Majority Leader Mitch McConnell said opening arguments in Trump's impeachment trial will begin Tuesday.

The Democrat-authored impeachment articles charge Trump with abuse of power and obstruction of Congress stemming from his alleged misconduct toward Ukraine. Democrats say Trump abused his presidential power by allegedly pressuring Ukraine to investigate Democratic rival Joe Biden, using military aid to the country as leverage.

Donald Trump has become the third American president to be impeached. Trump has been charged with abuse of power and obstruction of Congress. Led by Democrats, the U.S. House of Representatives passed the articles of impeachment on Dec. 18, 2019. Trump will face trial in the GOP-controlled Senate in 2020, a presidential election year. Presidents Andrew Johnson and Bill Clinton were also impeached. Neither was removed from office.

Trump is also charged with obstructing Congress’ ensuing probe.

The House approved transmitting the articles by a party-line vote of 228-193 about 1:30 p.m. Wednesday. The impeachment managers hand-delivered the impeachment articles to the Senate on Wednesday evening.

»Meet the House impeachment managers

On Wednesday morning, House Speaker Nancy Pelosi named seven impeachment managers, Democrats who will attempt to convince the Senate that Trump is guilty and should be removed from office.

Trump impeachment moves forward

“This is what an impeachment is about,″ Pelosi said before the vote. “The president violated his oath of office, undermined our national security, jeopardized the integrity of our elections.”

Trump’s political campaign dismissed the House effort as “just a failed attempt to politically damage President Trump leading up to his reelection.”

House Minority Leader Kevin McCarthy said Americans will look back on this “sad saga” that tried to remove the president from office with the “weakest case.”

The president’s team expects acquittal with a Senate trial lasting no more than two weeks, according to senior administration officials unauthorized to discuss the matter and granted anonymity.

»MORE: Which U.S. presidents have faced impeachment?

That’s far shorter than the impeachment trial of President Bill Clinton, in 1999, or the first one, of President Andrew Johnson, in 1868.

President Bill Clinton was impeached on perjury and obstruction of Congress charges on Dec. 19, 1998. He was acquitted by the Senate on Feb. 12, 1999. Fourteen senators from that trial still remain in office. Here's how they voted. Susan Collins, R-Maine. Not guilty on both counts Michael D. Crapo, R-Idaho. Guilty on both counts Richard Durbin, D-Illinois. Not guilty on both counts Mike Enzi, R-Wyoming. Guilty on both counts Dianne Feinstein, D-California. Not guilty on both counts Charles Grassley, R-Iow

McConnell pledged to have the Senate “rise above the petty factionalism” and “factional fervor and serve the long-term, best interests of our nation.″ He called it “a difficult time for our country.”

Ahead of Wednesday's session, Rep. Adam Schiff released new records from Lev Parnas, an associate of Trump lawyer Rudy Giuliani, about the Ukraine strategy, including an exchange with another man about surveilling later-fired Ambassador Marie Yovanovitch.

»MORE: GAO: White House violated law by holding back aid for Ukraine

Schiff said the new evidence should bring more pressure on McConnell, who is reluctant to allow witnesses to testify and prefers swift acquittal. The White House has instructed officials not to comply with House subpoenas for testimony and documents.

U.S. House Democrats have drafted two articles of impeachment against President Donald Trump. House leaders are charging the president with abuse of power and obstruction of Congress. They announced the articles of impeachment on Dec. 10, 2019. A full House impeachment vote could come before Christmas. If passed, the president would face a Senate trial in 2020, a presidential election year.

“The challenge is to get a fair trial,” Schiff said in an interview with The Associated Press. “It shouldn’t be a challenge — if the senators are really going to live up to their oath to be impartial, they’ll want a fair trial. That’s obviously not where Mitch McConnell is coming from.”

Those or any four senators could force an outcome. Republicans control the chamber 53-47 and are all but certain to acquit Trump. But it takes 51 votes during the trial to approve rules or call witnesses. It also would take only 51 senators to vote to dismiss the charges against Trump.

Impeachment was established in the U.S. Constitution as a way to accuse a president of a crime and then hold a trial to determine if guilty. The first step requires a U.S. House member to introduce an impeachment resolution. The House speaker directs the judiciary committee to hold a hearing to decide whether to put the full measure to a vote by the full chamber. A majority of the committee must approve the resolution. If approved, it moves to a full vote on the House floor. If a majority of the House vot

Pelosi had been unsuccessfully pressuring Senate leaders to meet her impeachment trial demands, which include hearing from witnesses who were not called during the Democrat-led House impeachment hearings.

»MORE: Who are the major players in an impeachment trial? 

Specifically, Democrats are hoping to call more witnesses during a Trump impeachment trial than they did during House proceedings, citing new evidence of Trump’s alleged misconduct.

In the weeks since Trump was impeached, Democrats have focused on new evidence about Trump’s alleged effort to pressure Ukraine to investigate his political rivals, and they pushed the Senate to consider new testimony, including from former White House national security adviser John Bolton.

McConnell has advocated for weeks that a Trump impeachment trial would follow the same model as Clinton's in 1999.