You don't think that the president has Due Process constitutional rights?
Not in an impeachment trial. This is not a court of law as we imagine such and is not bound by any rules of evidence or due process. It is a strictly political affair and can use any rules that the Senate wishes.
The best rule they could adopt is to immediately dismiss all charges as unfounded and irrelevant. As in "these charges do not rise to the level of high crimes or misdemeanors". End of story.
If they do conduct a "trial", the longer it runs, the greater the chance they will vote to remove President Trump. The Senate is as corrupt as the House and too many Republicans still want to keep the gravy train running for themselves. They will make deals with the Democrats if they think they can keep it quiet. Hence the trial balloons about a "secret ballot" for the impeachment.
But if the promised payouts are big enough, the Republicans will betray President Trump quite openly with the thinnest of legal pretenses. They actually believe they could collect what they are being promised.
In the event of a conviction, I would expect Civil War II to go hot immediately.