Republicans in the Senate insist that they will not bring any Obama nomination to replace Justice Scalia to the floor for a vote. They want the next president to nominate a replacement, obviously in the belief that the next president will be Republican.
The danger for them is that if Clinton wins the election she may just nominate Obama to the vacancy on SCOTUS, and if the Senate tilts towards Democrats in November, she may just succeed in getting him confirmed.
Republicans will then be stuck with Obama for a long time to come – sort of like a continuation of his presidency.
Republicans should beware of playing constitutional games, especially since the current crop of Republican candidates seem highly unlikely to beat Clinton or Sanders in the elections.