Not that the guy is a conservative, but he's a less reliable liberal than someone a new Democratic president might appoint, especially since there's a good chance a Democratic President would bring in a Democratic Senate.
So, don't dismiss the guy. Just drag it out until the lame duck period after the election. If Hillary or Bernie wins, then confirm the guy so they don't get to appoint their guy. And if the Republican wins, either vote him down or don't vote on him. Let the new GOP resident pick his guy.
In trying to pick a more moderate guy (at least on the surface) Obama may have given some Republicans a good strategic option.