If the Democrats call the Republican witness, that do have first hand knowledge of what trump did, depending what the Chief Justice does, will set the tone for the trial. It will show if Trump has bought the high court or not. The Democrats should have tried to enforce their subpoenas through the courts. Even if it took a year or more, we would then have a definitive ruling stating that congressional subpoenas are enforceable or not. This was a very short sighted decision that will have to go through the courts at some time. Better sooner than later.