Having nominated Merrick Garland to the Supreme Court March 16, 2016, and with the United States Senate having failed to make timely assertion of the right to provide advice and consent, President Obama should now appoint Garland and direct him to take his position as Justice of the Supreme Court. The Senate would then be free to sue the President and make the case that this action is not in keeping with Article II. Such a suit would presumably be accepted by the Supreme Court with Garland recusing himself. It would be interesting to see how the eight member Court rules.
See the April article in the Washington Post by Gregory L. Diskant to get the constitutional argument. I think everyone who agrees needs to do whatever possible to urge this action.