I found it very telling that even the Republicans' witness at the hearing,
Jonathan Turley, a law professor at George Washington University, said he doesn’t support Trump and voted against him.
The Republican witness, Jonathan Turley, presented himself as an impartial observer. “I am not a supporter of President Trump,” he said in his written testimony. “I voted against him in 2016 and I have previously voted for Presidents Clinton and Obama.”
Nor did he argue or even hint that what Trump is accused of is not valid grounds for impeachment, only that he thought the process was being rushed, and needed more supporting evidence. Unfortunately for Trump, however, the evidence (which is already compelling, despite what Turley said) is still accumulating, and almost none of it favors Trump. One of the main reasons there isn't even more evidence is that Trump has illegally forbidden any in his administration to testify, even if lawfully subpoenaed by Congress. If he is as innocent as he claims, why not let his people testify? The answer is increasingly obvious, as those few who have defied that order and testified under oath, so far, have almost invariably (if not always) offered testimony that hurt more than helped his case.
The Republicans can't and barely even attempt to offer exculpating evidence for Trump, and instead try to malign and destroy the integrity of the witnesses, no matter how sterling their reputation and record of prior patriotic service, and attack the impeachment process itself. The best they can do is try to argue that Trump's grievous misconduct is not really impeachable, which is a rather stupid hill to die on.