We present the first direct evidence that state-level public opinion on whether a particular Supreme Court nominee should be confirmed affects the roll-call votes of senators. Using national polls and applying recent advances in opinion estimation, we produce state-of-the-art estimates of public support for the confirmation of 10 recent Supreme Court nominees in all 50 states. We find that greater home-state public support does significantly and strikingly increase the probability that a senator will vote to approve a nominee, even controlling for other predictors of roll-call voting. These results establish a systematic and powerful link between constituency opinion and voting on Supreme Court nominees.
My guess is that a lot of the causation runs in the other direction. Had 20 Republican Senators reacted to Sonia Sotomayor’s nomination by saying “she sounds like a great pick,” she probably would have been extremely popular right out of the gate. One of the virtues of party discipline is that it sends a message to both that party’s self-identified supporters and also to the self-consciously moderate.