Chief Justice John Roberts and the senators who will serve as jurors were sworn in Thursday for the Trump impeachment trial, as the historic proceedings opened in the Senate with a mix of pageantry and partisan swipes.

"Senators, I attend the Senate in conformity with your notice for the purpose of joining with you for the trial of the president of the United States," Roberts said, before Iowa Sen. Chuck Grassley, the president pro tempore, administered the oath to him.

Roberts then immediately swore in the senators, who will act as the jury in the trial. And one-by-one, each senator took turns approaching the well of the Senate to sign an oath book.

Earlier on Thursday, House Sergeant-at-Arms Paul Irving led a procession of Democratic "managers" across the Capitol and the upper chamber formally received the articles of impeachment.

At noon, the Senate recognized the House managers who will prosecute the case against President Trump. The body then began a formal presentation of the two articles of impeachment brought against him: charges of abuse of power and obstruction of Congress.

"Hear ye, hear ye, hear ye: All persons are commanded to keep silent on pain of imprisonment, while the House of Representatives is exhibiting to the Senate of the United States articles of impeachment against Donald John Trump, president," Irving said on the Senate floor.

It marks the third impeachment of a president in U.S. history.

Grassley, the president pro tempore, presided over the Senate, as the House managers were welcomed and Rep. Adam Schiff, D-Calif., began reading the resolution.

As the articles of impeachment left a bitterly divided House, both sides took parting shots at each other at back-to-back press conferences.

Minority Leader Rep. Kevin McCarthy, R-Calif., blasted the partisan impeachment as “taxpayer-funded campaign stunt.” He railed against House Speaker Nancy Pelosi, D-Calif., for an impeachment signing event with souvenir pens, when she’s said all along impeachment must be solemn and prayerful.

"If this was real, if this was really as serious as they claimed this would be, yesterday was no cause for celebration,” McCarthy said.

Pelosi, however, said the president’s actions gave the House “no choice” but to impeach Trump and bashed Senate Republicans who would reject a trial without witnesses and documents.

“They’re afraid of the truth,” Pelosi said, calling impeachment a “sad day for America.”

“The president necessitated this by his abuse of power and his obstruction of congress,” Pelosi said, pointing to new evidence brought forth by Lev Parnas, the Rudy Giuliani associate who said he helped Trump pressure Ukraine for political favors, and a new government finding that the Trump administration violated the law by withholding aid from Ukraine. Read more at FOX News