The timing could not be worse for the GOP, but the court cannot be left deadlocked for more than a year simply because the GOP is being childish. Doing so would clearly show that the GOP is only too happy to damage the country to get their way. Refusing to govern in a presidential election year, with 24 GOP Senate seats to defend would be a huge mistake. If they do, and they might, they will lose the Senate, lose the White House, and lose the chance to name the next SC Justice.
If McConnell follows through, refusing to allow an Obama's nomination to come to the Senate floor for a vote, he will be creating the longest vacancy in the history of the 9 man court. That will leave the left leaning 8 justice court to make crucial decision over the next year and possibly much longer if there's a democrat elected. Clearly the Republican Senate is placing their political aim of a more conservative court above their constitutional duty.
If the court has a tie vote on a case, then the ruling of previous federal court will stand. Court decisions can have a huge impact. Suppose the court was called to make a decision that would determine the presidency as they did with Bush vs. Gore and could not reach a decision.
Clearly the Republican Senate is placing their political aim of a more conservative court above their constitutional duty.