The House of Representatives impeached President Donald Trump on Dec. 18 on two charges: abuse of power and obstruction of Congress.

It’s now up to a trial in the Senate to determine if those charges — officially called articles — merit removing Trump from the presidency. Presidents Andrew Johnson and Bill Clinton were tried and acquitted by the Senate in 1868 and 1999, respectively.

The ceremonial start to the third trial of a sitting president began Jan. 16. The trial resumes Wednesday at 1 p.m. with opening arguments.

Here’s a look at how the process will unfold:

What’s already happened

7 managers

Seven House lawmakers, who are called “managers” will prosecute the case against Trump. They brought the articles of impeachment to the full Senate on Jan. 16 and read the charges aloud. From left to right: Adam Schiff, Zoe Lofgren, Jerry Nadler, Jason Crow, Val Demings, Sylvia Garcia, Hakeem Jeffries.

Chief Justice

Supreme Court Chief Justice John Roberts was sworn in and will preside over the the trial.

The Senate

“I do,” the members of the full Senate affirmed to an oath read by Roberts.

Oath the 100 senators take Do you solemnly swear that in all things appertaining to the trial of the impeachment of Donald John Trump, president of the United States now pending, you will do impartial justice according to the Constitution and laws, so help you God? Quote icon

The trial begins

Senate Majority Leader Mitch McConnell, R-Ky., reopened the trial on Tuesday with a marathon Senate session that stretched into early Wednesday and answered some key questions:

How many hours does each side have to make their case?

Both sides will have 24 hours over three to days to argue their cases.

How long will senators have for questions?

After the two sides present their cases, senators have 16 hours to ask questions.

What about witnesses or documents?

After the questions, the senators can vote to issue subpoenas for new witnesses or documents they deem necessary.

Rules decided

A 51-vote majority was needed to decide the rules, and no one in the 53-Republican majority broke ranks to join with the Democrats and their amendments to McConnell's proposed rules.

House managers present case

Trump is accused of soliciting foreign interference in the 2020 election by asking Ukraine to investigate his political rival. During a July 25 phone call, Trump urged Ukrainian President Volodymyr Zelensky to investigate former Vice President Joe Biden, whose son Hunter once sat on the board of a Ukrainian energy company.

Trump attorneys present defense

From left to right: Pat Cipollone, Jay Sekulow, Alan Dershowitz, Ken Starr, Robert Ray, Pam Bondi, Patrick Philbin, Jane Raskin, Michael Purpura and Eric Herschmann. More on Trump's team.

The president's legal team said in brief filed Monday that the two articles of impeachment against Trump "do not identify any impeachable offense;" the House impeachment inquiry was "irredeemably flawed," and there is "no evidence" to back the House impeachment claims.

What's ahead

Senators are not allowed to speak during the trial. Now that the two sides have made their arguments, senators have up to 16 hours to ask questions in writing, which Roberts will read.

The House managers and Trump’s defense present closing arguments.

Decision time for senators

The senators could call for closed session to discuss the evidence or discuss options such as censure that would leave Trump in office, but voice Congress’ concerns with his actions.

The votes

The senators will vote on both articles of impeachment. A two-thirds majority of the Senate would be required to convict and remove Trump, which is unlikely in the chamber where Republicans outnumber Democrats 53 to 47.

The verdict

Photos by AP; Getty Images; Joyce Naltchayan/AFP via Getty Images; Kasowitz Benson Torres LLP; and William Pratt, U.S. Army.