To the lawyer types on here. Is discovery allowed in this trial?
The senate makes the rules on a case by case basis. Any discovery will be on the Senate's terms. Likewise with putting on the case, and putting on a defense. The Senate can limit all of this by time, or by number of witnesses, or whatever it wants. The process can be just as lopsided as the House. What controls this is the Senate desire to maintain the illusion it is being deliberative, fair, and reaching the right outcome.
It'll be a real show! Under Clinton, leader and minority worked together to set up the trial parameters. Who knows how much McConnell will concede to Schumer. Could be little or nothing, could be everything Schiumer wants, he gets, and McConnell limits the defense as much as he thinks his relelection can stand.
The GOP desperately wants to be returned to minority status. It does not want a return to constitutional government. It is a gloabalist institution, and GOP "principles" are just for show, not for go.