Jonathan Turley The second impeachment trial of Donald Trump appeared to effectively end before it even began Tuesday. In a threshold procedural vote on the constitutionality of trying a former president, 45 senators voted in favor of a motion to challenge the trial, and that means almost half of the Senate believes Trump might not be subject to a trial, let alone a conviction, as a former president. It also means House impeachment managers may not be able to secure the Senate votes to convict. For those members who believe the trial…