You might classify the views on such matters in terms of two pure positions. One is the view Senator Chuck Schumer (D, NY) has been consistent in holding (although his application of it leaves much to be desired, in my view). According to him, there is absolutely nothing wrong with expecting nominees to violate the current norm among judicial nominees not to comment on potential future cases or on issues one expects might come before the court one will be seated on. In the Roberts and Alito hearings, he pressed for details on whether they believe certain rights are established in the Constitution, whether they would be willing to overturn certain precedents, whether they thought particular cases were wrongly decided, and so on. They refused in many of these cases to go beyond the standard they both believed to have been presented by now-Justice Ginsburg's nomination process a decade-and-change earlier. Their reasoning is that commenting on what may be central to forthcoming cases will threaten their perception as unbiased judges, since those whose cases will be heard will think the justices' minds are already made up and will not give them a chance. But this is not the reasoning of the other pure view on such matters.
The alternative view is not merely that there is a convention among judges not to engage in such prediction out of fairness to parties in future cases. The alternative pure view is that it is simply not the business of the Senate in confirming judicial nominees to engage in partisan politics. That is for the president to be concerned with, since it is his election that determined who would nominate judges for any vacancies. The Senate's role is merely to safefuard the president's choices against serious corruption and ethical issues and to ensure that the nominees are qualified to carry out the tasks required of them. Deference is given to the president's nominee. The primary objection to this view is that the Senate is also an elected body, and they are elected for partisan reasons to present partisan considerations for or against what the Senate might do, including for or against judicial nominees in their role of advising and consenting. It is thus within their authority to question nominees who are both qualified and not corrupt simply because they disagree with the nominee on issues of legal philosophy.
I think the latter issue is an interesting debate in constitutional interpretation. The Constitution's text merely says that the Senate will advise and consent to the president's nominees. It doesn't give a reason why. It doesn't indicate what process the Senate will engage in before giving their consent or their advice. It doesn't say if the advice and consent are different stages of a two-step process. Those things are all not in the text of the Constitution but are in the Senate's current practice of carrying out this role. I don't know anything about the legal background to this sort of thing and whether English common law explains it. I don't know anything about the debates in the constitutional committees over this language and what light that sheds on it. I don't know anything about whether the federalist papers explain what some of the founders were thinking of as they argued for this kind of wording. In short, I am woefully unqualified to have much of a view about what the Constitution really means by saying this. If I were to go by what I take from it merely by reading the words, I'd be inclined to think that the Senate ought to give advice to the president and then confirm whoever the president selects.
But I'm sure it doesn't mean something so strong, since there's no point in having the Senate consent if there's no legal means for them to withhold consent. But it does appear to say that the Senate will consent (not that they should decide whether to). So I take my reading as inadequate, mainly because I know that the authors of the Constitution weren't complete idiots, and my reading of what it says sounds like something only an idiot would put in a constitution. But that does leave a lot of room between those who think only a small set of criteria are grounds for senatorial rejection of nominees to those who think senators can reject a nominee merely because they don't like how they look.
Now aside from the constitutional issue, there's a separate question as to which approach is better. Again, I'm not sure I can offer much, mainly because I can see a point to both sides. The basic issue up for debate is whether (1) a president should be given deference in judicial choices because it is a matter for the executive branch to select judges, with the legislative branch merely serving to make sure there aren't any good non-political reasons to oppose those nominations or (2) the legislative branch's purpose in being involved is no to rubber-stamp executive branch decisions on judicial nominees but to limit how extreme those judges might be by not approving of judges they don't agree with on judicial matters. Thus for a judge to get on the bench they will need to be chosen by a president and (in effect) approved of by a highly partisanly-divided panel of senators before ultimately being approved by the whole Senate (which is much more moderated than the Judiciary Committee, most of whose members are toward the harder right and left of their side of the committee).
I tend to think the current balance and methods would lead to very bad results if the second view is taken. The Judiciary Committee does not reflect the balance of the Senate, not remotely. The main tactic of both parties has been to hold nominees in committee (but using different methods; the filibuster was new with the Democratic opposition to G.W. Bush nominees, for instance). The reason is that they know the majority of the Senate would approve the nominees, so they have to stop that vote from happening using tricks with the rules of the Senate to stop a floor vote. But isn't the Senate as a whole given this advise-and-consent role, not the small part of the Senate that holds hearings on judiciary nominees?
This is what leads to great frustration from the nominating party, which right now is the GOP but in a couple years may well be the Democrats. The politicization of the nomination process thus leads committees to say things out of context, to take select cases out of hundreds where a few words here or there can be misinterpreted, taken apart from a much wider support for the principles the nominee is taken to deny, and so on. This is the lowest of tricks.
I could rattle off lots of examples from the nomination hearings for Chief Justice Roberts and Justice Alito, and I've been reading about a number for the latest hearing for Leslie Southwick for an appeals court nomination. The accusations have been highly immoral. I'm glad Senator Feinstein saw through it in Southwick's case, because it was really evil what they were doing to him, e.g. insinuating that he's a racist merely because he believes the law and state Supreme Court precedents he was interpreting have a different impact on the case in question than the other judges did and because he refused to give policy arguments as to why to interpret the law a certain way. I do not hesitate to say that Senator Durbin's comments on this man's character were downright evil, just as I don't hesitate to say the same of Senator Kennedy's statements about then-Judge Alito a couple years ago. I don't have a long enough history of following politics to know any examples of Republicans doing the same thing with Clinton nominees, but I won't rule out the possibility that that happened, and I know human nature well enough to suspect that it probably did happen, even with senators whose official views do not allow such behavior.
This scene is not good. I don't want to see this sort of thing happen, and I do think it is a fairly direct result of having partisan senators evaluating judicial nominees by a president of the opposing party, given the depth of evil that human nature contains. This is exactly the kind of thing I'd expect evil people to do in such situations, and since every human being is evil to the core, it's what we get in such heated situations.
Is there a way to avoid that? I think there is, and it actually reveals a middle-of-the-road position on the first issue I was discussing. I presented the two pure views and the main considerations offered against them. I believe the mediating position I'm about to present can handle both objections while capturing some of what both positions originally wanted at the outset.
Pure position 1 is that nominees should freely give all their views on any matter asked about related to how they'd decide cases. The problem is that it would threaten a preceived bias in cases related to those issues if they were to comment on matters that would come before them on the bench.
Pure position 2 is that nominees should be evaluated based on their qualifications rather than their judicial philosophy and thus should not be expected to comment on individual cases or issues that may come before the court, because the Senate's role in judging nominees is to prevent the president from having too significant a role without the Senate's check and balance. The problem is that there are political reasons to allow the Senate to serve as more of a check and balance than that.
Now either problem may turn out to be not as significant as those who present it think. But it occurs to me that there's a way to resist both problems without endorsing either view as stated. On this mediating view, nominees should not be expected to comment on individual cases, but they should be expected to be able to present a judicial philosophy. Despite what Senator Schumer has recently been claiming, there's no way to argue that senators had little information on the latest two Supreme Court justices, since their records revealed quite a bit about the kinds of reasoning they engage in, and senators did ask them questions about how they arrived at those decisions.
Why couldn't judicial nominees also comment on the reasoning that appeared in particular cases that they didn't decide? What they need to avoid is taking a stance on actual cases that could appear before their court, but they can comment on general matters that would pertain to such cases, and they can comment on previous Supreme Court cases in terms of whether it was good or bad reasoning.
According to this view, it's fair game to say whether a certain decision was wrongly or rightly decided and what would have been better reasoning if any. It's fair game to comment on what considerations might go into overturning a particular precedent without indicating (as a promise) what one will do, allowing for all manner of alternative considerations to weigh a decision in a different direction. I could say why I think a certain case was wrongly decided while remaining open about whether I'd overturn it. I can also say that I think there's a reason for overturning it while remaining open about other reasons not to overturn it that I may not even have considered. As long as it's kept at that level, you would get some discussion of more substantive issues than what has happened recently. Yet it wouldn't be the politicized mess that we have been getting either.
(Well, we might still have senators lying and saying, for example, that a pretty moderate conservative like Alito is way outside the mainstream. But it might diminish how often they might lie about their character or attribute to them views they don't have. There would be little reason to lie if they could simply vote against them because of their judicial philosophy rather than because of fabricated ethical failings.)
Would this be a better result? In some ways, yes. One result I would appreciate less is that the Supreme Court would become less diverse. Any nominee who could be approved by a Senate whose party is not the president's would have to be fairly moderate. But I think moderate conservatives such as Alito and Roberts could get enough Democratic votes to get in, as they did in the closely-divided battles they actually faced. I suspect the same is true of moderate liberals such as Breyer. Would that result be better or worse? I'm not sure. But it's worth considering. I'm curious what additional arguments people can come up with for favoring this, keeping the status quo, or providing an alternative solution.