John Kastellec, Jeff Lax, and Justin Phillips write:

Do senators respond to the preferences of their states’ median voters or only to the preferences of their co-partisans? We [Kastellec et al.] study responsiveness using roll call votes on ten recent Supreme Court nominations. We develop a method for estimating state-level public opinion broken down by partisanship. We find that senators respond more powerfully to their partisan base when casting such roll call votes. Indeed, when their state median voter and party median voter disagree, senators strongly favor the latter. [emphasis added] This has significant implications for the study of legislative responsiveness, the role of public opinion in shaping the personnel of the nations highest court, and the degree to which we should expect the Supreme Court to be counter-majoritarian. Our method can be applied elsewhere to estimate opinion by state and partisan group, or by many other typologies, so as to study other important questions of democratic responsiveness and performance.

Their article uses Mister P and features some beautiful graphs.