He'd do less damage to the Constitution than would another Souter.
There may well come a time when there are five lawless judges on the Court. When that time comes, the only hope for the Republic will be for a significant portion of the populace to realize that although what the Constitution says, and what the Supreme Court says, will be one and the same when the court is doing its duty, there is nothing in the Supreme Law of the Land which gives the Supreme Court any authority to issue decisions contrary to it, much less anything which says such decisions should be regarded as superior to the Constitution.
The more overtly political the Court's leftist judges are, the more accepting people will be of the notion that an overt willingness on the part of some of the justices to ignore the Constitution does not change the Supreme Law of the Land. If in some case five judges openly ignore the Constitution, there may not be any remedy for the actual parties to that case, but nor is there any basis for declaring that the Constitution means the things claimed by judges who are overtly disregarding it.
I don't trust him either and I'd make him give up a short list of potential nominees.