The detailed and emotional presentation by Democrats was followed by meandering and occasionally confrontational arguments from the Trump defense team, which insisted that his remarks were protected by the First Amendment and asserted that he cannot be convicted as a former president. Even Trump’s backers in the Senate winced, several saying his lawyers were not helpful to his case.

The senators sitting as jurors, many of whom fled for safety themselves the day of the attack, watched and listened, unable to avoid the jarring video of Trump supporters battling past police to storm the halls, Trump flags waving. While many minds are made up, the senators will face their own moment to decide whether to convict or acquit Trump of the sole charge “incitement of insurrection.”

The heavy emotional weight of the trial punctuates Trump’s enduring legacy as the first president to face impeachment trial after leaving office and the first to be twice impeached. The Jan. 6 Capitol siege stunned the world as hundreds of rioters ransacked the building to try to stop the certification of Democrat Joe Biden’s victory, a domestic attack on the nation’s seat of government unlike any in its history. Five people died.

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 “That’s a high crime and misdemeanor,” Rep. Jamie Raskin, D-Md., declared in opening remarks. “If that’s not an impeachable offense, then there’s no such thing.”

Trump’s lawyers insist he is not guilty, his fiery words just figures of speech.

In a key early test, senators rejected an effort by Trump’s allies to halt the trial, instead affirming the Senate’s authority under the Constitution to decide the case. They voted 56-44 to confirm their jurisdiction, ruling that impeaching a president after he leaves office is constitutionally permissible. Six Republicans joined the Democrats.

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Security remained extremely tight at the Capitol on Tuesday, a changed place after the attack, fenced off with razor wire and with armed National Guard troops on patrol. The nine House managers walked across the shuttered building to prosecute the case before the Senate.

White House press secretary Jen Psaki said Biden would not be watching the trial of his predecessor.

“Joe Biden is the president, he’s not a pundit, he’s not going to opine on back and forth arguments,” she said.

With senators gathered as the court of impeachment, sworn to deliver impartial justice, the trial started with the Democratic House managers’ gripping recollections, as they described police officers maimed in the chaos and rioters parading in the very chamber where the trial was being held.

Also read: 5 key questions for Trump’s Senate impeachment trial

Trump’s team countered that the Constitution doesn’t allow impeachment at this late date. Though the trial now proceeds, that’s a legal issue that could resonate with Republicans eager to acquit Trump without being seen as condoning his behavior.

Lead lawyer Bruce Castor said he shifted his planned approach after hearing the prosecutors’ opening and instead spoke conversationally to the senators, saying Trump’s team would do nothing but denounce the “repugnant” attack and “in the strongest possible way denounce the rioters.” He appealed to the senators as “patriots first,” and encouraged them to be “cool headed” as they assess the arguments.

Trump attorney David Schoen turned the trial toward starkly partisan tones, saying the Democrats were fueled by a “base hatred” of the former president.

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Republicans made it clear that they were unhappy with Trump’s defense, many of them saying they didn’t understand where it was going -- particularly Castor’s opening. Louisiana Sen. Bill Cassidy, who voted with Democrats to move forward with the trial, said that Trump’s team did a “terrible job.” Maine Sen. Susan Collins, who also voted with Democrats, said she was “perplexed.” Sen. Lisa Murkowki of Alaska said it was a “missed opportunity” for the defense.

The early defense struggles also underscored the uphill battle that Trump’s lawyers face in defending conduct that preceded an insurrection that senators themselves personally experienced. Though they will almost certainly win Trump’s acquittal — by virtue of the composition of the Senate — they nonetheless face a challenge of defanging the emotion from a trial centered on events that remain raw and visceral, even for Republicans.

At one pivotal point, Raskin told his personal story of bringing his family to the Capitol the day of the riot, to witness the certification of the Electoral College vote, only to have his daughter and son-in-law hiding in an office, fearing for their lives.

“Senators, this cannot be our future,” Raskin said through tears. “This cannot be the future of America.”

The House prosecutors had argued there is no “January exception” for a president to avoid impeachment on his way out the door. Rep. Joe Neguse, D-Colo., referred to the corruption case of William Belknap, a war secretary in the Grant administration, who was impeached, tried and ultimately acquitted by the Senate after leaving office.

If Congress stands by, “it would invite future presidents to use their power without any fear of accountability,” he said.

On the vote, six Republicans joined with Democrats pursue the trial, just one more than on a similar vote last week. Cassidy joined Collins, Murkowski, Mitt Romney of Utah, Ben Sasse of Nebraska and Pat Toomey of Pennsylvania. But the total of 56 was still far from the two-thirds threshold of 67 votes that would be needed for conviction.

It appears unlikely that the House prosecutors will call witnesses, in part because the senators were witnesses themselves. At his Mar-a-Lago club in Florida, Trump has declined a request to testify.

Also read: Trump parts with impeachment lawyers a week before trial

Presidential impeachment trials have been conducted only three times before, leading to acquittals for Andrew Johnson, Bill Clinton and then Trump last year.

Because of the COVID-19 crisis, senators were allowed to spread out, including in the “marble room” just off the Senate floor or even in the public galleries, but most were at their desks.

Presiding was not the chief justice of the United States, as in previous presidential impeachment trials, but the chamber’s senior-most member of the majority party, Sen. Patrick Leahy of Vermont.

Under an agreement between Senate Majority Leader Chuck Schumer and Republican leader Mitch McConnell, the substantive opening arguments will begin at noon Wednesday. The trial is expected to continue into the weekend.

Trump’s second impeachment trial is expected to diverge from the lengthy, complicated affair of a year ago. In that case, Trump was charged with having privately pressured Ukraine to dig up dirt on Biden, then a Democratic rival for the presidency.

This time, Trump’s “stop the steal” rally rhetoric and the storming of the Capitol played out for the world to see.

The Democratic-led House impeached the president swiftly, one week after the attack. Five people died, including a woman shot by police inside the building and a police officer who died the next day of his injuries.

Timothy Naftali, a clinical associate professor at New York University and an expert on impeachment, said in an interview, “This trial is one way of having that difficult national conversation about the difference between dissent and insurrection.”