The irony is stifling. For months, McConnell and other Republicans complained that the impeachment process was being rushed, the president was being denied basic procedural protections, and that there was no testimony from those with the most direct knowledge of Mr. Trump’s actions and motivations. Then they refused to hear from a single witness and refused to demand a single document from the White House, a vote that was tantamount to an acquittal of the impeachment charges. The vote brings the nation face to face with the reality that the Senate has become nothing more than an arena for the most base and brutal — and stupid — power politics. Faced with credible evidence that a president was abusing his powers, it would not muster the institutional self-respect to even investigate.Every impeachment trial in American history had included witnesses.