WASHINGTON – Sen. Mazie Hirono, D-Hawaii, has said she's ready to convict President Donald Trump at his impeachment trial that starts next week. Sen. Lindsey Graham, R-S.C. is a staunch ally of the president who has called the charges a "sham."
On Thursday, they joined the chamber's 98 other senators in taking a constitutionally required oath "to do impartial justice according to the Constitutions and laws" in the impeachment trial of Trump over his attempts to get Ukraine to publicly investigate political rival Joe Biden.
But can Hirono, Graham and many of the other senators who have expressed strong views about the president's conduct really be unbiased? And can they be punished if they betray that oath?
The answers may not be known until the trial is over and a verdict rendered.
It takes at least two-thirds of the Senate, or 67 votes, to convict Trump on the two charges filed by the House – abuse of power and obstruction of Congress – and remove him from office. Nobody expects that to happen in the GOP-controlled Senate where Republicans occupy 53 of the 100 seats.
Majority Leader Mitch McConnell, R-Ky., has made it clear he's not pretending to be objective in what will be only the third impeachment trial of a president ever held in the Senate.
"I'm not an impartial juror. This is a political process. There's not anything judicial about it," the Kentucky Republican told reporters in December. "I would anticipate we will have a largely partisan outcome in the Senate. I'm not impartial about this at all."
In response, the watchdog group Public Citizen filed a complaint with the Senate Ethics Committee earlier this month against McConnell to determine whether the majority leader's recent statements violate his oath as well as the rules of the Senate requiring impartiality. The complaint seeks a determination on whether he should recuse himself from the impeachment proceedings.
The oath is applied any time the Senate considers removal of a judge, a president or a fellow senator. It requires each one to swear or affirm that they will “do impartial justice according to the Constitution and laws.
The oath was originally adopted by the Senate before proceedings in the eventual expulsion of Senator William Blount of Tennessee in 1798 and has remained largely unchanged since, according to the Congressional Research Service.
During the nation's first presidential impeachment trial in 1868, the oath aided Andrew Johnson's acquittal by giving senators justification to follow legal guidelines, not their own political interests, according to scholars Karlyn Kohrs Campbell and Kathleen Hall Jamieson.
“What the oath established was that each senator was answerable for his vote, not to his constituents or his party, but to the law, the Constitution, and to God,” they wrote in “Presidents Creating the Presidency.” “The `impartial justice’ to which each senator was pledged was the justice the president’s defenders were calling for.”
Most senators would never get to serve if this were a regular courtroom since they've already publicly prejudged Trump's guilt or innocence, said Joel Cohen, a lawyer with Stroock & Stroock & Lavan and co-author of “I Swear: The Meaning Of An Oath.”
But because there is no mechanism for easy removal in an impeachment trial, no senator is expected to be disqualified, he wrote in a column for Bloomberg Law.
"Given that specific requirement of 'impartiality,' the oath taken by virtually every senator will be false, whether or not he or she has spoken publicly to the issue," Cohen argued. "So here’s the real question. What’s the true value of an oath that unambiguously demands `impartiality' when partiality on both sides has decided the case before the proceedings begin?"
The oath requires that senators maintain "a veil of ignorance" as if they didn't know the party affiliation of the president being impeached, George Washington University experts Ira C. Lupu and Robert W, Tuttle wrote in a blog for The Hill newspaper.
"This includes evaluating the evidence, and deciding whether the proven misconduct justifies removal from office," they wrote. "Senators violate their oath if they apply friendlier standards to Presidents of their own Party than to those of the opposing Party ... Any Republican Senator who would vote to remove a Democratic President for such misconduct must, by their Oath, vote to remove Trump."
Previous impeachment trials show lawmakers are expected to use their own judgment on how to follow the oath.
During a 2010 trial of a judge, the Senate trial committee noted that there is no set standard of proof of wrongdoing so each senator could use the standard he or she felt was appropriate.
Lawmakers, the Congressional Research Service noted, “have sought to ensure that individual members remain free to make their own determinations, guided by their individual conscience and judgment, and their oath to do `impartial justice.’”
As for punishment, experts say that will ultimately be left up to voters in the next election who will decide whether they acted appropriately and deserve another term.
Sen. Tim Kaine, D-Va., urged senators should take their oaths seriously.
"As individuals, we may have biases, but that special oath implies profound trust that we will remove ourselves from the partisan passion of the moment and exercise judgment with sole regard for impartial justice," he wrote in a column for USA TODAY.
"Senators McConnell and Graham made their promises of partiality before they swore the oath that they will be required to swear in a few days. Nothing gives them an excuse for violating their own oaths" Kaine wrote. "For the good of the country, they should rethink their position before they stand in front of the American public and make a promise they intend to evade."