If Trump is the Republican nominee, they'll lose any chance they have of winning the Presidency, and will almost certainly lose the Senate. Then, any leverage they have is gone. A President Clinton (or Sanders) will undoubtedly nominate someone more liberal than anybody Obama picks.

If Trump sweeps today and pretty much wraps up the nomination, I anticipate that desperate Republican Senators will start falling all over themselves trying to make a deal with Obama before the Senate essentially shuts down for campaign season. Once again, Obama has masterfully allowed bumbling Republicans to paint themselves into a corner!!