Romney was able to appoint liberals in MA, because it was...well..Massachussetts. He was probably encouraged and rewarded for doing so.
He would have a much tougher time doing that as president.
All I know is that one more nomination from Obama could seal our fate for the next 25 years. A quarter century, in which states rights, abuse of commerce clause, made up abortion rights, etc. will not suffer the scrutiny of a supreme court case. That’s a guarantee. A second term Obama would nominate somebody to the left of Ginsburg.