I have not said much about the impeachment trial for the same reason I didn't say much about the impeachment itself, beyond some basics (I, II): there is, despite the volume of words said about it, not much to be said. It seems to me, however, that some people have repeatedly set themselves up for disappointment through not recognizing that trying an impeachment is very different from what we generally call a trial. The basic distinction between an impeachment trial and an ordinary trial is written into the Constitution, such that if someone is impeached and convicted for X, this does not constitute the trial for X under law. (This was a modification of the British process that was specifically introduced into the American process.) While impeachment is like indictment, it is not strictly an indictment, but what is substituted in its place, and there are a number of differences between the two from the very beginning.
But there are other changes that follow from the structure of such a trial. The Senate has to be under Oath for it (the usual reason given for this historically is to create an incentive for Senators not to act vindictively); when the President is tried, the Chief Justice is required to preside (to prevent the trial from being presided over by the Vice President); no one may be convicted without 2/3 of the members present (another obvious deviation from the British process that was usually thought to have been introduced to reduce the chances of conviction on purely partisan grounds). Other than that, it is an act of the Senate and thus all rules governing it are determined by the Senate. There are no procedural rules, except what the Senate determines. There are no rules of evidence, except what the Senate determines. There are no burdens or standards of proof, except what Senators in voting decide to use. This is because, not being a trial in the normal sense, impeachment is not only concerned with the office-holder only as an office-holder, it is not concerned with legal punishment but with political punishment. The primary question before the Senate in an impeachment trial is, "Given the charges, should someone be removed from office who is in that office due to a legitimate, constitutional, and thus authoritative exercise of power?" In the case of the President, of course, that means removal of someone serving a fixed term for which he was elected. Being guilty in this context is to have done something to convince the legislature that authority given by the electorate through a constitutional process must be taken away. And everything revolves around that.
Even when the President is of an opposing party, this is a hard sell, in part because Senators have to face the electorate that put the President in power and thus have to be sure that they are not going to be removed at the end of their own term for not instead leaving the whole matter to voters themselves. It has never been a likely scenario that Senators of the same party as the President would in any significant number vote to remove the President, short of charges capable of turning a significant number of presidential supporters against him; since Trump's polling numbers are notoriously stable, the charges quite clearly do not do that, particularly since Republicans are quite clearly worried about Democrats trying to use this as a platform for attacking Republicans across the board -- I mean, it's inevitable in an election year that they will do this, but Republicans are worried about having to deal with it under conditions in which they would also be handing Democrats advantages in doing so. Senators are not always perfectly predictable, so we will see later this week what the actual results are, but the two-thirds is not in the cards.
Given all this, nothing has passed with respect to the trial itself that should have been unexpected, particularly given the Senate Majority Leader's unusually acute talent for always finding the way of proceeding that is least convenient for the political goals of the Democrats in Congress, nor can the trial ever have been considered much more than a political version of a Hail Mary pass, in the hope of something, anything, creating a hard shift in the political situation. Again, while we will see the precise result later this week, it seems clear enough that absolutely nothing has.
