Washington • Senators are sworn in. Chief Justice John Roberts has the gavel. And the impeachment trial of President Donald John Trump is set to start.

The Senate will begin to hear arguments Tuesday about why Trump should be removed from office for high crimes and misdemeanors and a defense of why he’s innocent of the charges, sprinkled with questions of whether witnesses should be called or new evidence considered.

Brace yourself.

For a somber and historic moment, it’s going to be wild.

While senators have pledged to be impartial, politics will likely drive the trial with Trump’s hand-picked defense team making the case that he did nothing wrong, or at least nothing impeachable, and Democrats charging that the president has abused his power and obstructed Congress in a scheme that hurt national security in an attempt to help his own interests.

Here's a look at how the trial will unfold — at least as it's supposed to go.

How does it work?

Basically, the Senate is a jury and will weigh the evidence presented by a team of House members countered against a defense offered by Trump's lawyers.

Tuesday begins with opening arguments by the House managers, as they're called, a discussion that could span several days, depending on a debate over rules that could take up some time.

There's likely to be a motion to dismiss the charges outright, though that is doomed to fail, as well as a motion to include witnesses, a move that may not initially earn any GOP support.

Senators are supposed to check their phones at the door and remain in their seats during the trial. They can ask questions, albeit in writing and funneled through Roberts, who, under the Constitution, presides.

Trump’s team comes next. And given that his team — which includes former Florida Attorney General Pam Bondi, Harvard law professor emeritus Alan Dershowitz and former independent counsel Ken Starr — is playing for an audience of one, that would be Trump, it might make interesting TV.

It takes only a majority of senators to set or change the rules, or overturn a decision by Roberts, and that's the key part of the trial to watch.

Democrats, who control 47 seats if you include two independents who caucus with them, will want to call witnesses, and a handful of GOP senators, including Sen. Mitt Romney, R-Utah, have said they are open to that.

Even as Senate Majority Leader Mitch McConnell of Kentucky has said he was working with the White House on the trial's parameters, he doesn't want to make the proceedings look like a sham.

That said, it takes 67 votes to remove the president from office, a threshold that, short of explosive new evidence, isn’t likely.

Anticipated events in connection with impeachment of President Donald Trump.

What role will Utah senators play?

Romney, a former GOP presidential nominee who has been at times a Trump critic, is a wild card in the trial. While the Utah Republican may support many of the president’s policies, he’s no Trump fan.

Romney isn't likely to join some of his GOP colleagues in offering a full-throated Trump defense and has said that he will be impartial.

Romney told The Salt Lake Tribune last week that he wants to follow the process the Senate used during the impeachment of President Bill Clinton 20 years ago. That included open arguments, followed by a vote on allowing witnesses.

“That's a process I support,” Romney said.

The senator added that he wouldn't back an expected motion to allow witnesses from the outset — “I will oppose that, even though I anticipate I will want witnesses down the road.”

Romney has said he at least wants to hear from former National Security Adviser John Bolton, who has stated he would testify if subpoenaed.

And Romney said he wouldn't entertain the idea of dismissing the case at the beginning.

“I don't know whether that motion will ever see the light of day,” Romney said.

Groups already are lining up to support or oppose senators, depending on how they handle the trial. One anti-Trump, Republican group is going to air ads on TV and digital platforms as well as erect a billboard calling on Romney to fulfill his pledge to hear from witnesses.

Sen. Mike Lee, R-Utah, is in another category.

“It has been reported in the media that I am working behind the scenes to help acquit the president. Politico calls me ‘a quiet force and one of the de facto leaders of the case to clear the president,’” Lee wrote on Facebook recently. “The reason I am working so closely with the White House on this issue is because the President has every reason to be confident about this, every reason to be unapologetic and defiantly confident about his case.”

Lee, who declined to comment last week outside the Senate chamber, said he has a goal for the outcome of the trial, and he’s unabashedly laying it out.

“And you know what we’re going to do? We’re going to embarrass the heck out of the Democratic Party because they’ve been an embarrassment in the way that they’ve handled this,” Lee wrote. “The president’s going to win — and win in a big way.”

Will Trump win?

It’s hard to imagine a scenario where the Senate would actually remove Trump from office. The past two presidents facing Senate impeachment trials were acquitted. Trump is likely to be the third.

Republicans hold enough of a majority that it would take incredibly damning information to persuade 20 GOP senators to switch their votes to convict Trump.

Removing a president from office is also a drastic step that polls show isn't extremely popular with Americans overall.

That said, House Speaker Nancy Pelosi, D-Calif., has essentially anticipated the Senate result.

She and fellow Democrats have repeated the line that Trump will forever carry the asterisk of impeachment into the history books.

This president is impeached for life regardless of any gamesmanship on the part of Mitch McConnell,” Pelosi said on ABC’s “This Week.” “There is nothing the Senate can do to ever erase that.”

How long will this last?

Good question. That's one thing nobody really knows.

The trial could last a couple of weeks, or longer if witnesses are allowed. And partisan bickering will be on overdrive.

The impeachment proceedings will begin every day at 11 a.m. Mountain Time so that senators can do some of the country's business in the morning.

The Senate has placed severe restrictions on news media coverage of the trial, limiting where reporters can stand to ask questions, limiting the number of journalists allowed in the Senate hallways and banning laptops and phones inside the gallery overlooking the chamber. The TV feed of the trial Americans will see will also be controlled by Senate staffers.