Senator Cory Booker (D-NJ): "The president of the United States is a subject of an ongoing criminal investigation...that could end up before the Supreme Court," so any Trump SCOTUS nomination should be "delayed until the Mueller investigation is concluded."
From a Senate Judiciary Committee meeting on Thursday:
SEN. BOOKER: If we are not going to thoroughly discuss what it means to have a president with this ongoing investigation happening who is now going to be able to interview Supreme Court Justices and potentially with his tradition of doing litmus tests, loyalty tests for that person we could be participating in a process that could undermine that criminal investigation.
I think it is in the best interest of our democracy for this committee to consider a nominee from a president -- I think it is questionable that we should be considering a nominee from a president who has a history of demanding these loyalty tests and we could be responsible for participating in something that could undermine that investigation.
I do not believe that this committee should or can in good conscience consider a nominee put forward by this president until that investigation is concluded. Not only do I believe that we should abide by the rule set by [Majority Leader] McConnell, but I think we should look at the larger moment that we're in American history and that conflict of interest that is clearly present in this president.
Booker also said the president could pick a Justice to "protect himself."
"Should we be confirming a justice that's going to be coming from a person, frankly, that there's a conflict of interest there, that this judge could end up having to preside over cases relevant to this criminal investigation? ... I say no," Booker said Thursday evening on MSNBC.