Citing the Washington Post article "Obama can appoint Merrick Garland to the Supreme Court," given that Merrick Garland is a pre-eminent legal scholar and has been previously called a "consensus nominee" by Republicans, Obama should send the Senate a notice saying that if they haven't acted on the nomination in 90 days they will have waived their rights to the process, and he will be appointed.
This will force the Senate to bring legal suit, wherein the Supreme Court will eventually decide (with Mr. Garland recusing himself) the proper course of action of the Senate in situations as this.
This will be the best attempt Obama can make at filling the court and will establish legal precedent in the US for if and when a situation like this happens again.
Spread this quickly!! Time is short!