WASHINGTON — Searing images of lawmakers ducking behind chairs in fear for their lives, fleeing the House chamber as rioters closed in, and a police officer crying out in pain played Tuesday in the U.S. Senate, where lawmakers began an unprecedented second impeachment trial of Donald Trump.

The former president, Democratic impeachment managers argued, must be held accountable for the months of incitement that led to those violent scenes of the Jan. 6 insurrection at the Capitol, and can’t escape responsibility simply because he is no longer in office. Trump’s attorneys countered that it is vindictive and against the Constitution to try him now that he is out of office.

Allowing former officials to escape impeachment and conviction would give congressional approval to future attempts to subvert elections, said Rep. Jamie Raskin (D., Md.), adding that presidents are bound by their oaths for every day they serve. If presidents are allowed to escape punishment because they commit misdeeds just before leaving office, he said, days like Jan. 6 will “become our future.”

“It’s an invitation to the president to take his best shot at anything he may want to do on his way out the door, including using violent means to lock that door, to hang on to the Oval Office at all costs, and to block the peaceful transfer of power,” said Raskin, the lead impeachment manager prosecuting the House case against Trump. “In other words, the January exception is an invitation to our founders’ worst nightmare.”

Trump’s attorneys, in an often rambling response that went long stretches without touching on the substance of the case, said impeachment was based simply on Democrats’ disdain for Trump and his voters, and also raised concerns about due process.

“This is a process fueled irresponsibly by base hatred,” said David Schoen, one of Trump’s lead attorneys, “and they are willing to sacrifice our national character to advance their hatred and their fear that one day they might not be the party in power.”

He said a conviction would disenfranchise Trump voters by barring Trump from running for office again, and would “tear this country apart, perhaps like we have only seen once before in our history.”

» READ MORE: First it was ‘fraud,’ then they just didn’t like the rules: How Pa. Republicans justified trying to overturn an election

(Trump and his GOP allies had actively sought to disenfranchise the entire electorate in several states, including Pennsylvania, by leveling false fraud claims and attempting to throw out those states’ Electoral College votes).

The arguments around constitutionality made up the opening act as the Senate began the fourth presidential impeachment trial in American history, the first of a former president, and the first of a president who had been impeached twice. It marked yet another chapter in Trump’s grip on the country’s attention and politics.

Democrats and six Republicans voted 56-44 to proceed with the trial, with Sen. Pat Toomey (R., Pa.) among the GOP lawmakers to support moving forward. One Republican, Sen. Bill Cassidy of Louisiana, changed his stance after hearing the arguments from both sides and voted to support the trial’s legality.

But the vote also signaled that Democrats face almost impossible odds to secure the 67 votes needed to convict Trump. It would take 17 Republicans joining every Democrat to do so.

“The result of this trial is preordained,” Sen. Ted Cruz (R., Texas) said. “President Trump will be acquitted.”

Schoen’s presentation followed an opening argument from Bruce Castor, another Trump attorney and a former Montgomery County commissioner and district attorney. Castor’s opening drew criticism and ridicule from even GOP senators who oppose the trial and intend to acquit Trump.

» READ MORE: Bruce Castor had a big spotlight to open Trump’s impeachment defense. It didn’t go well.

“I thought the house impeachment managers made very strong arguments. It was persuasive and well-grounded in the Constitution and precedent,” said Toomey, who has signaled he is open to voting to convict. As for the defense, he said: “I think they had a weaker case to start with, and I don’t think it was very persuasive.”

The 100 senators sat quietly throughout most of the proceedings, many rapidly scribbling notes as they reprised an exercise most went through early last year when Trump was acquitted after his first impeachment. Outside, uniformed National Guard troops carrying high-powered rifles continued guarding the Capitol, barely a month after the deadly attack by a pro-Trump mob left five dead.

Democrats argued that impeachment is necessary to hold Trump accountable for one of the darkest moments in recent American history.

Raskin and his fellow Democrats quoted numerous legal scholars, some of them conservative and long tied to Republican politics, who argued that precedent and a plain reading of the Constitution show that a former president can, in fact, stand trial. They pointed to statements made during the writing of the Constitution, and to past impeachment trials of former office holders (though not presidents) to support their case.

But they also appealed to raw emotion, showing a 13-minute video of the insurrection, splicing together Trump’s words with horrific scenes of the violence, including the moment when a Capitol police officer shot and killed a rioter trying to climb through a door outside the House chamber.

» READ MORE: Montco’s Bruce Castor and Madeleine Dean bring very different approaches to Trump’s impeachment trial

”You ask what a high crime and misdemeanor is under our Constitution,” Raskin said after the video. “That’s a high crime and misdemeanor. If that’s not an impeachable offense, then there’s no such thing.”

Most senators watched with tensed brows, though with one screen set up in each corner, Democrats turned to their left, Republicans to their right — each literally looking at the scene in opposing directions. Several Republicans, including Sens. Marco Rubio of Florida and Tom Cotton of Arkansas, largely looked away from the violence, keeping their focus on papers in front of them.

Raskin closed by recounting how colleagues and aides placed phone calls and texts on Jan. 6 saying goodbye to loved ones. It was just days after a funeral for one of his sons, who had died by suicide, and his daughter and her husband hid under desks in the Capitol complex, believing they might now die, Raskin recalled. He broke into tears when describing how his daughter told him she wouldn’t want to return to the building.

“This cannot be the future of America,” he said.

Even Cruz praised Raskin’s presentation, though other Republicans dismissed appeals to emotion, and said they would rule based on their readings of the law.

Republican senators had few kind words for Castor, who worked off a handwritten legal pad and said the Trump team changed its plans at the last minute because the Democrats’ opening had been so strong.

Cassidy said that as a juror, after hearing the arguments he had no choice but to change his stand on the constitutionality of the trial.

“President Trump’s team was disorganized, they did everything they could but to talk about the question at hand,” Cassidy said shortly after voting to proceed with the trial.

» READ MORE: Bruce Castor’s impeachment trial speech spawns memes and confusion

Yet most Republicans, even those who joined that criticism, still made clear they would not vote to convict Trump, hewing to the argument that the Senate can’t convict a former president.

“This isn’t just about Donald Trump, this is about setting a precedent,” said Sen. John Cornyn (R., Texas).

Schoen, after blasting the Democrats’ motives, turned to more legalistic arguments, making the case that the House rushed its impeachment without hearings or a full investigation.

“God forbid we should ever lower our vigilance to the principle of due process,” Schoen said.

Even as he chided Democrats for moving too fast, however, he also argued that the language of the Constitution shows that it’s now too late to try Trump, since he is out of office.

» READ MORE: Fact-checking Trump’s false claims about Pennsylvania’s election before his supporters attacked the Capitol

While the arguments Tuesday largely centered on the constitutionality of the case, its origins are tied to the political fight for Pennsylvania, one of the most hotly contested presidential battlegrounds, and one where Trump falsely claimed that fraud caused his defeat. Pennsylvania was one of just two states, along with Arizona, whose electors faced a debate and vote on Jan. 6, the day Trump staged his rally and urged his supporters to “fight like hell” before they rampaged through the Capitol, in some cases chanting to hang then-Vice President Mike Pence.

Republicans have mostly refused to defend Trump’s conduct leading up to the attack, but the vast majority have also signaled that they are highly unlikely to convict him.

Both parties appeared eager to quickly put the trial behind them. Democrats, realizing they are highly unlikely to convict Trump, want to keep approving President Joe Biden’s nominees and advancing his agenda as he seeks to take advantage of his opening months in office.

Republicans appeared loath to dwell on the riot and Trump’s actions.