Here’s how that would work. The president has nominated Garland and submitted his nomination to the Senate. The president should advise the Senate that he will deem its failure to act by a specified reasonable date in the future to constitute a deliberate waiver of its right to give advice and consent. What date? The historical average between nomination and confirmation is 25 days; the longest wait has been 125 days. That suggests that 90 days is a perfectly reasonable amount of time for the Senate to consider Garland’s nomination. If the Senate fails to act by the assigned date, Obama could conclude that it has waived its right to participate in the process, and he could exercise his appointment power by naming Garland to the Supreme Court.
Presumably the Senate would then bring suit challenging the appointment. This should not be viewed as a constitutional crisis but rather as a healthy dispute between the president and the Senate about the meaning of the Constitution. This kind of thing has happened before. In 1932, the Supreme Court ruled that the Senate did not have the power to rescind a confirmation vote after the nominee had already taken office. More recently, the court determined that recess appointments by the president were no longer proper because the Senate no longer took recesses.
It would break the logjam in our system to have this dispute decided by the Supreme Court (presumably with Garland recusing himself).