On February 13th, Supreme Court Justice Antonin Scalia passed away. Just over a month later, on March 16th, President Obama nominated Merrick Garland, a man who is more than qualified, to fill the vacancy on the court. He then submitted said nomination to the Senate for its advice and consent, per the United States Constitution. Since then, Senate Republicans have refused to even hold a hearing on the nomination, much less vote on its consent.
In doing so, the Senate has made the decision not to advise on or consent to the nomination, giving, through inaction, ultimate discretion to the President.
It is now not only the ability, but the constitutional obligation of President Obama to appoint Garland, filling the vacancy on the court.