Pence's outrageous op-ed holds deeper meaning

For only the third time in American history, the US Senate has opened a trial for an impeached president. On Thursday, Supreme Court Chief Justice John Roberts administered a special oath to all senators, requiring that they "do impartial justice" in their judgment of the president's alleged "high crimes and misdemeanors." What does that mean in practice, when the Senate is so divided by party, with a majority leader who has promised to coordinate closely with the impeached president?