WASHINGTON (NewsNation Now) — Senators were sworn in as jurors Tuesday for the impeachment trial of former President Donald Trump that’s slated to begin early next month.

The swearing-in ceremony is the next requirement after the House delivered an article of impeachment to the Senate Monday. It sets the stage for a historic trial against Trump, the first U.S. president to be impeached twice and the first former president to face an impeachment trial after leaving office.

In a 55-45 vote, the Senate on Tuesday also rejected an attempt by Republicans to declare the trial unconstitutional.

The move comes the day after nine Democratic House impeachment managers – who will serve as prosecutors in the trial – carried the sole charge of “incitement of insurrection” across the Capitol in a solemn and ceremonial procession. The lead House prosecutor, Rep. Jamie Raskin of Maryland, then read the House resolution charging “high crimes and misdemeanors” before the Senate.

A growing number of Republican senators are voicing their opposition to the trial. Some are questioning the constitutional authority to convict a president after their term has ended, while others say it further stokes party divisions.

Republican Sen. John Cornyn, of Texas, asked if Congress starts holding impeachment trials of former officials, what’s next: “Could we go back and try President Obama?”

He suggested that Trump has already been held accountable. “One way in our system you get punished is losing an election,” he said.

Senate Majority Leader Chuck Schumer, a Democrat, rejected that argument on Monday.

“The theory that the Senate can’t try former officials would amount to a constitutional get-out-of-jail-free card for any president,” Schumer told the Senate.

Still, such arguments may signal the dimming chances that Republicans will agree with Democrats in convicting Trump on the charge that he incited a siege of the U.S. Capitol earlier this month.

The Senate is divided 50-50, with Democrats holding a majority because of the tie-breaking vote of Vice President Kamala Harris. Democrats would need the support of 17 Republicans to convict Trump.

The Senate trial is expected to begin the week of Feb. 8, after leaders in the chamber agreed to delay it two weeks to give Trump more time to prepare a defense and let senators focus on Biden’s early priorities.

Democrat Patrick Leahy, the Senate’s longest-serving member, said on Monday he would preside over the trial.

Although the Constitution calls on the U.S. chief justice to preside over presidential impeachments, a senator presides when the impeached is not the current president, a Senate source said. First elected to the chamber in 1974, Leahy, 80, holds the title of Senate president pro tempore.

Chief Justice John Roberts presided over the impeachment trial when the Senate, then controlled by Trump’s fellow Republicans, acquitted Trump in February 2020 on charges of abuse of power and obstruction of Congress arising from his request that Ukraine investigate Biden and his son.

Leahy will still be able to vote in the trial, an aide said, noting that senators still vote on all matters when presiding over the chamber.

The Associated Press and Reuters contributed to this report.