No, President Obama CANNOT appoint Merrick Garland to the Supreme Court if the Senate does nothing
Over the weekend, Gregory Diskant suggested in a Post op-ed that President Obama could unilaterally appoint Judge Merrick Garland to the Supreme Court if the Senate fails to act on his nomination. My co-blogger Ilya Somin has explained why Diskant is mistaken. I would add a few points to Ilya's critique.
First, the idea that the Senate has an affirmative duty to act in order to reject or "veto" a nomination does not square with the original understanding of the Appointments Clause. As Adam White has explained, the original understanding of the Founders considered, and ultimately rejected, a proposal to require the Senate to affirmatively reject a nomination in order to prevent a confirmation. Moreover, as Chief Justice Marshall noted in Marbury v. Madison, nomination and appointment are separate actions. Under the text of the Appointments Clause, the former is the president's alone, while the latter is conditioned on Senate action.
Second, consistent practice establishes that the Senate may exercise its power to offer or withhold advice and consent in whatever manner it chooses. Over the course of the nation's history, the Senate has exercised this power in many different ways, sometimes rejecting nominees outright, but other times filibustering or simply refusing to consider nominees the Senate did not wish to confirm.
In some cases, the Senate has refused to act because it did not like the nominee in question. In other cases, the Senate has refused to act for reasons that have nothing to do with the nominee, such as a belief that a position need not be filled, disagreement with the president on some other matter, for political leverage, or even to keep a seat vacant until after an intervening election. Law professor Lillian BeVier was nominated to the U.S. Court of Appeals for the Fourth Circuit in October 1991, and the Senate never took any steps to consider her nomination, keeping the seat open until President George H.W. Bush left office. Alas, this is not an isolated example.
Some might argue that the Supreme Court is different, but there is only one Appointments Clause, and the ninth seat on the Supreme Court (like seats on lower courts and principal officer positions in the executive branch) only exists because it was authorized by Congress. Thus there is no textual or structural reason to treat this vacancy differently from others, and many structural reasons to reject the idea that the president could ever unilaterally fill a lifetime appointment to a coordinate branch without Senate cooperation. Harvard law professor Matthew Stephenson has argued that the president should be able to fill the most important executive branch positions where the Senate refuses to act, but he expressly considered, and rejected, the idea that this should apply to the judiciary. (To be clear, I am not endorsing Stephenson's analysis, just noting that he would not take it as far as Diskant does.)
Third, the argument that the president could act unilaterally to fill a vacancy in response to Senate intransigence is even more aggressive (and outrageous) than the Obama administration's argument that it could define what constitutes a "recess" triggering the president's authority to fill vacancies with recess appointments. The Supreme Court rejected this argument 9-0 in Noel Canning v. NLRB, even though this could enable the Senate to keep important vacancies open for extended periods of time. The power to define what constitutes a recess, the court concluded, lies with the Senate. Just as Congress determines what constitutes a recess, it is up to the Senate to determine what constitutes "advice and consent." This principle finds further support in Nixon v. United States (that's Walter Nixon, not Richard), which explained why it would be inappropriate to allow other branches to define or interfere with the exercise of the legislative branch's checks on the judiciary.
Finally, let me note that Ilya and I are hardly the only ones to reject Diskant's position. The article has prompted derision and scorn from quite a few informed observers across the political spectrum. On the right, Ed Whelan assailed the op-ed's "gobsmacking stupidity" on NRO's Bench Memos. On the left, Ian Millhiser of the Center for American Progress tweeted: "I want Democrats to gain a majority on the Supreme Court more than I love life itself. But this argument is dumb." Other commentators were equally unimpressed with Diskant's "bad argument," including professors Christopher Walker, Eric Segall, and our own Orin Kerr.
The bottom line is simple. The argument that the president could simply appoint a nominee to the Supreme Court when the Senate refuses to act is even weaker—far weaker—than the erroneous argument that the Senate has an obligation to act in the first place. It is an argument that is extremely hard to take seriously.