The impeachment battle is shifting to the Senate ahead of a weeks-long trial expected to get underway next week.

With the House voting Wednesday to transmit the articles, Chief Justice John Roberts and senators are expected to be sworn in on Thursday. A fierce rules fight and opening arguments will get started on Tuesday.

Though the outcome of the trial is pre-baked, the high-profile proceeding, the third in the chamber’s history, will put a spotlight on a handful of key potential swing votes, as well as the 2020 contenders.

ADVERTISEMENT

Here are seven things to know.

McConnell to make it as ‘painful’ as possible

Senators are getting a list of strict rules they have to follow once the trial starts.

According to decorum guidelines circulated Wednesday, senators will not be able to bring electronic devices on the floor, speak to others while on the floor or bring reading material unless it’s related to impeachment.

They are expected to be in their seats as they listen to House managers and Trump’s team make their respective cases. Senate Rules Committee Chairman Roy Blunt Roy Dean BluntCDC tells Congress it urgently needs billion for vaccine distribution On The Money: Trump undercuts GOP, calls for bigger COVID-19 relief package | Communities of color hit hardest financially by COVID-19 | Businesses, states pass on Trump payroll tax deferral Trump undercuts GOP, calls for bigger COVID-19 relief package MORE (R-Mo.) said they will not be allowed to use video evidence, something House Democrats wanted.

The Senate will also be in session six days a week, a stark difference from the chamber’s normal Monday evening to Thursday afternoon schedule.

ADVERTISEMENT

Sen. John Cornyn John CornynBipartisan praise pours in after Ginsburg's death Chamber of Commerce endorses McSally for reelection Airline job cuts loom in battleground states MORE (R-Texas), who said late last year that he hoped Senate Majority Leader Mitch McConnell Addison (Mitch) Mitchell McConnellObama calls on Senate not to fill Ginsburg's vacancy until after election Planned Parenthood: 'The fate of our rights' depends on Ginsburg replacement Progressive group to spend M in ad campaign on Supreme Court vacancy MORE (R-Ky.) would agree to let them work only five days a week, told The Hill that he saw no signs the GOP leader was prepared to back down from the more demanding work schedule.

Another GOP senator, asked about the possibility, told reporters recently that he assumed McConnell “will want it to be as painful as it can possibly be” to keep senators focused on getting through the trial.

Witnesses are the wildcard

The biggest unknown: Will 51 senators ultimately decide to call witnesses?

Republican senators are expected to pass a rules resolution that would punt the decision until after opening arguments and questions from senators. The resolution, according to GOP senators who have seen it, will require a vote at the end of the first phase on whether to call witnesses.

Democrats want to hear from acting White House chief of staff Mick Mulvaney Mick MulvaneyMick Mulvaney to start hedge fund Fauci says positive White House task force reports don't always match what he hears on the ground Bottom line MORE, former national security adviser John Bolton John BoltonDiplomacy with China is good for America The Hill's Morning Report - Sponsored by The Air Line Pilots Association - Pence lauds Harris as 'experienced debater'; Trump, Biden diverge over debate prep DOJ launches probe into Bolton book for possible classified information disclosures MORE, Mulvaney’s senior adviser Robert Blair and Michael Duffey, the associate director of national security at the Office of Management and Budget.

They’ll need four Republican senators to support their request. Sen. Mitt Romney Willard (Mitt) Mitt RomneySenate Republicans face tough decision on replacing Ginsburg McConnell says Trump nominee to replace Ginsburg will get Senate vote GOP-led panel to hear from former official who said Burisma was not a factor in US policy MORE (R-Utah) has specifically said he wants to hear from Bolton and anticipates voting for him to testify.

Sens. Susan Collins Susan Margaret CollinsSenate Republicans face tough decision on replacing Ginsburg Democratic senator calls for eliminating filibuster, expanding Supreme Court if GOP fills vacancy What Senate Republicans have said about election-year Supreme Court vacancies MORE (R-Maine) and Lisa Murkowski Lisa Ann MurkowskiSenate Republicans face tough decision on replacing Ginsburg What Senate Republicans have said about election-year Supreme Court vacancies McConnell says Trump nominee to replace Ginsburg will get Senate vote MORE (R-Alaska) are also viewed as potential swing votes. They said Wednesday it is too soon to determine which witnesses should testify.

“There will be this time in the process where we will have an opportunity to make a determination as to what further information we need, whether it is for Hunter Biden or Ambassador Bolton,” Murkowski said.

Conservatives are threatening to force tough votes on testimony from Biden and the whistleblower who triggered impeachment if their Republican colleagues vote to subpoena Bolton.

Democrats, Trump face off for first time

Speaker Nancy Pelosi Nancy PelosiPelosi: Ginsburg successor must uphold commitment to 'equality, opportunity and justice for all' Bipartisan praise pours in after Ginsburg's death Pelosi orders Capitol flags at half-staff to honor Ginsburg MORE (D-Calif.) on Wednesday announced the seven Democrats who will be responsible for arguing the lower chamber’s case, with House Intelligence Committee Chairman Adam Schiff Adam Bennett SchiffTop Democrats call for DOJ watchdog to probe Barr over possible 2020 election influence Overnight Defense: Top admiral says 'no condition' where US should conduct nuclear test 'at this time' | Intelligence chief says Congress will get some in-person election security briefings Overnight Defense: House to vote on military justice bill spurred by Vanessa Guillén death | Biden courts veterans after Trump's military controversies MORE (D-Calif.), who spearheaded the impeachment inquiry, leading the team.

ADVERTISEMENT

House Judiciary Committee Chairman Jerrold Nadler Jerrold (Jerry) Lewis NadlerTop Democrats call for DOJ watchdog to probe Barr over possible 2020 election influence House passes bill to protect pregnant workers House Democrats postpone vote on marijuana decriminalization bill MORE (D-N.Y.) and Reps. Hakeem Jeffries Hakeem Sekou JeffriesPelosi: House will stay in session until agreement is reached on coronavirus relief Races heat up for House leadership posts Postmaster general earned millions from company with ties to Postal Service: report MORE (D-N.Y.), Val Demings Valdez (Val) Venita DemingsFlorida Democrat introduces bill to recognize Puerto Rico statehood referendum Sunday shows - Trump team defends coronavirus response Demings slams GOP coronavirus relief bill: Americans 'deserve more than the crumbs from the table' MORE (D-Fla.), Zoe Lofgren Zoe Ellen LofgrenTop Democrats call for DOJ watchdog to probe Barr over possible 2020 election influence DHS opens probe into allegations at Georgia ICE facility House passes legislation to boost election security research MORE (D-Calif.), Sylvia Garcia Sylvia GarciaHispanic Caucus asks for Department of Labor meeting on COVID in meatpacking plants Texas Democrat proposes legislation requiring masks in federal facilities Hispanic Caucus requests meeting with private detention center CEOs MORE (D-Texas) and Jason CrowJason CrowClark rolls out endorsements in assistant Speaker race Trump-Afghan deal passes key deadline, but peace elusive Cook shifts 20 House districts toward Democrats MORE (D-Colo.) were also named.

Meanwhile, White House counsel Pat Cipollone will lead Trump’s defense team, with the president’s personal attorney Jay Sekulow Jay Alan SekulowNow, we need the election monitors Judge denies Trump's request for a stay on subpoena for tax records Judge throws out Trump effort to block subpoena for tax returns MORE acting as his No. 2. Whether Trump will try to add House Republicans to his team remains an open question.

Senators get to ask questions

Senators are expected to be able to submit questions through Roberts, who will read them aloud.

The Senate used two days during the 1999 Clinton trial to answer more than 150 questions submitted to then-Chief Justice William Rehnquist. Senators in 1999 had 16 hours for questions, and lawmakers say they expect the rules for Trump’s trial to give a similar amount of time.

Cornyn and Sen. Ted Cruz Rafael (Ted) Edward CruzSenate Republicans face tough decision on replacing Ginsburg Cruz: Trump should nominate a Supreme Court justice next week Renewed focus on Trump's Supreme Court list after Ginsburg's death MORE (R-Texas) both said they were unclear what the order would be for how their questions get asked by Roberts. The chief justice is expected to say as he asks the question which senator it originated from, setting up key moments to watch as reporters try to infer what swing votes are thinking.

ADVERTISEMENT

Expected to go past State of the Union, Iowa caucuses

Sen. Roy Blunt (R-Mo.), who initially predicted the trial would be over by the State of the Union, told reporters that he now expects the proceeding will stretch beyond the scheduled Feb. 4 address.

The first phase of the trial — initial arguments and questions from senators — is expected to last roughly two weeks. After that, senators will still need to make a decision on hearing from witnesses and, eventually, vote on convicting or acquitting Trump.

The new time frame also has implications for Democratic White House hopefuls, grounding several candidates through the Feb. 3 Iowa caucuses.

Press crackdown expected

ADVERTISEMENT

The Senate sergeant-at-arms and the Senate Rules Committee are preparing new press restrictions in the Capitol, sparking a backlash from reporters who warn it will interfere with their ability to cover the trial.

One restriction would require reporters to remain in press pens outside of the Senate chamber. They would not be able to leave the roped-in area to talk to senators.

Sen. John Kennedy John Neely KennedyMORE (R-La.) distanced himself from the proposed restrictions, calling them a “huge mistake” that “sends the wrong message.”

Most of the Senate’s deliberations are expected to be televised, though senators could go into “closed session,” where they would turn off cameras and remove reporters for a private discussion.

Trial will end in Trump acquittal

With 67 votes required to convict Trump and remove him from office, the Senate proceeding is all but guaranteed to end in his acquittal.

To convict Trump, Democrats would need 20 Republican senators, as well as their entire caucus. No Republican senator has said they view Trump’s actions as an impeachable offense.

But GOP senators also say they want to formally acquit Trump instead of dismissing the articles, even though the idea has been embraced by Trump. The rules resolution is not expected to include a built-in motion to dismiss, a break from the Clinton rules.

“There is little to no sentiment in [the] Republican conference for a motion to dismiss,” McConnell told reporters this week. “Our members feel that we have an obligation to listen to the arguments.”