Here's how I see this playing out. Obama's going to nominate someone decently qualified and moderately liberal, just as he's done in the past. The republicans will block the nomination out of fear of getting beaten in their next primary. Eventually, those running for office this cycle will realize that Trump is going to be the nominee and that they need to help him if they want to keep any of their own seats. In order to get republican voters to hold their noses and vote for him, they advertise that the only way to prevent a liberal supreme court is to elect Trump and the GOP.
However, the idea of the next president being "guaranteed" a supreme court pick drives up turnout in general, helping Sanders in both the primary and general election, and democrats in general. Once Sanders and a senate super-majority are elected, the senate sees their choice between Obama's moderate liberal supreme court justice and a Sanders pick, and vote to confirm Obama's nominee.
Of course this is all just speculation. What do you think? Is this absolutely 100% correct or is it the stupidest prediction you've ever heard? Leave a comment and let me know.