The oath senators just took at the start of the impeachment trial is essentially meaningless

• Chief Justice John Roberts administered an oath to all 100 senators on Thursday, overseeing as they swore to "do impartial justice" during President Donald Trump's Senate impeachment trial.
• But dozens of senators on both sides of the aisle have already promised to break that oath. Chief among them is Senate Majority Leader Mitch McConnell.
• "Everything I do during this, I'm coordinating with White House counsel," McConnell recently said. "The case is so darn weak coming over from the House. We all know how it's going to end. There is no chance the president is going to be removed from office."
• There's nothing in the rules governing the Senate's impeachment process that would allow Roberts or anyone else to ensure lawmakers uphold impartial justice.
• Visit Business Insider's homepage for more stories.

Chief Justice John Roberts administered an oath to all 100 senators on Thursday, overseeing as they swore to "do impartial justice" during President Donald Trump's Senate impeachment trial.

Every senator solemnly swore "that in all things appertaining to the trial of the impeachment of Donald John Trump, president of the United States, now pending, I will do impartial justice according to the Constitution and laws, so help me God."

But dozens of senators, on both sides of the aisle but particularly in the GOP, have already promised to break that oath. Chief among them is Senate Majority Leader Mitch McConnell.

"Everything I do during this, I'm coordinating with White House counsel," McConnell recently told Fox News' Sean Hannity of the impeachment trial. "The case is so darn weak coming over from the House. We all know how it's going to end. There is no chance the president is going to be removed from office."

Rather than insisting they'll keep their minds open to the evidence they're presented with - as a regular juror is required to do in a criminal trial - many senators are clear that they've made up their mind on how they'll vote.

And there's nothing in the rules governing the Senate's impeachment process that would allow Roberts or anyone else to ensure lawmakers uphold impartial justice.

Constitutional experts say the oath's lack of teeth is just further evidence of the political nature of the impeachment process the Founders designed.

Impeachment is a fundamentally political process - the Constitution stipulates that only Congress, rather than a court of law, can impeach and remove a president from office. Both Democrats and Republicans are vulnerable to political pressures - from the president to their constituents - which may well influence their vote.

Many Republicans argue Trump's impeachment is a partisan "witch hunt," so they see it as their responsibility to protect Trump from a political conviction. Democrats, meanwhile, may feel politically obligated to vote for removal.

Democrats have also previously interpreted the oath as permitting them to advocate on the president's behalf.

During former President Bill Clinton's 1999 impeachment trial, Chuck Schumer - now the Senate's minority leader - argued senators aren't required to be impartial in the traditional sense, calling the trial "a little bit judicial and a little bit legislative-political."

"The Founding Fathers, whose wisdom just knocks my socks off every day, it really does, set this process up to be in the Senate, not at the Supreme Court, not in some judicial body," Schumer said then. "Every day, for instance, hundreds of people call us up and lobby us on one side and the other. You can't do that with a juror. The standard is different. It's supposed to be a little bit judicial and a little bit legislative-political."

The Senate trial will officially resume on Tuesday, after lawmakers are given the day off on Monday to observe Martin Luther King Jr. Day.

The seven House impeachment prosecutors, also known as managers, will present the case against Trump first before Trump's team presents his defense.