Judicial Nomination Hearings and the Miers Example:
I enjoyed Jonathan's post below, and the Wittes article that he discuses, but it's interesting that Wittes doesn't mention the most recent example of how extensive open hearings can make a significant difference to the outcome of a nomination: the Supreme Court nomination of Harriet Miers.

  At least according to news reports, it was widely believed by around mid-October 2005 that the Miers nomination would stand or fall based on whether Miers could establish herself at the hearings as a fluent and well-informed voice on the Supreme Court and its jurisprudence. Her nomination was pulled for a few reasons, I gather, but, if reports are to believed, one of them was a sense that Miers would not thrive in the "kabuki dance" of live Senate hearings.

  If those reports are true, then I think that's an important data point to consider. Of course, how the example cuts depends on your view of the Miers nomination, about which reasonable people can differ. But I think it's important to view the role of hearings through the lens of all of the recent nominations, not just the ones that stayed viable through the period of Senate hearings.