And the Republicans control the United States Senate which will have to confirm a nomination.
There IS precedent for this.
Consider the following:
First, under the Senate's custom and tradition (known as the "Thurmond Rule,") action on the nomination of lifetime appointees customarily ceases during a presidential election year.
Second, for the past 80 years, no Supreme Court nominee whose name was placed in nomination during a presidential election year has been confirmed.
The Republicans are correct to insist that this nomination be made by the next president.
Finally, President Obama should take into account the reasoned judgement made by President Johnson in 1968 when he opted against an interim appointee to the high court after his nomination of Abe Fortas failed. NO confirmation now and NO interim appointment either.