First, Senate Minority Leader Charles Schumer (D-N.Y.) has already attempted the most straightforward. The Post reports:
In a letter to Senate Majority Leader Mitch McConnell (R-Ky.), Senate Minority Leader Charles E. Schumer (D-N.Y.) outlined a number of procedural demands that Democrats say would make the Senate trial fair and able to be completed “within a reasonable period of time.”
That includes subpoenas issued by Chief Justice John G. Roberts Jr. for acting White House chief of staff Mick Mulvaney; Robert Blair, a senior adviser to Mulvaney; former national security adviser John Bolton; and Michael Duffey, a top official at the Office of Management and Budget. Mulvaney, Blair and Duffey had been subpoenaed by the House committees and defied the summons; Bolton has not been subpoenaed but indicated he would fight one in court.
Second, if McConnell declines to reach agreement with Schumer, a group of Republican senators (three to deprive of a majority) can object to rules that do not incorporate most of Schumer’s proposals. This would take some political courage from Republican senators who claim to be interested in a factual inquiry and do not want to be seen as President Trump’s stooges. Sens. Mitt Romney of Utah, Susan Collins of Maine and Lisa Murkowski of Alaska would be some of those most likely to go along. (Even hinting that they would not agree to a sham trial might motivate McConnell to negotiate with Schumer in good faith.) However, there is certainly no guarantee that such a group will emerge.
Third, Speaker Nancy Pelosi (D-Calif.) could, after the House vote on the articles, decline to send over the articles until such rules for a real trial can be agreed upon. Give McConnell, say, 30 days to get this right. While the House makes clear that impeachment is urgent, there is no remedy for a clear and present danger in a farcical non-trial. Pelosi’s time frame could raise pressure on McConnell, further unhinge Trump and give Democrats a chance to get out there, as they have failed so far to do, with a full-blown ad campaign to convince voters of what is at stake.
Fourth, some have suggested that unless McConnell agrees, Pelosi should never send over the articles. The impeachment would be a permanent stain on Trump’s presidency, he would be denied his sham trial, and once more the Republicans’ contempt for the Constitution would be on full display. The risk, however, is that House Democrats become the constitutional malefactors in Republicans’ telling, that they lose the high ground and that they stand accused of wasting everyone’s time on impeachment.
I would prefer a fifth alternative, namely for Democrats to make a motion, appealing to Roberts., who will preside at the Senate trial, to allow for the presentation of evidence and issuance of subpoenas of key witnesses. Roberts could well decline, ceding to the Senate the right to make the rules, but at the very least, Republicans would have to publicly defend their sham. If, at the end of the proceedings, Democrats have not had access to witnesses, they could ask Roberts to declare a “mistrial.” That is highly unlikely to be granted, but it would cement in the public’s mind a key argument: The Senate did not acquit (or decline to remove) by a full and fair trial. The stain of impeachment should remain, Democrats can argue.
Finally, the backstop here is the voters — both in the form of peaceful demonstrations against Republicans’ blatant disregard of their constitutional oaths and at the ballot box, when those who refuse to honor their responsibilities as jurors can be tossed out.
That is the sequence that I would suggest Democrats follow, avoiding if at all possible a permanent refusal to send over the articles. Ultimately, the only guarantee rests with the voters, a fact not to be lost on Democratic primary voters as they choose the nominee best able to defeat Trump.