GOP Senators Rob Portman of Ohio and Pat Toomey of Pennsylvania have lined up behind Senate Majority Leader Mitch McConnell in saying they will not support anyone for the Supreme Court nominated by Obama. But that position isn't sitting well with their voters, especially moderate and independent voters though even GOP voters don't like that position. Polls show that refusing to not even consider a nominee will be remembered by voters in November. Both Toomey and Portman already have low approval ratings, though still higher than McConnell's approval rating. So this stance could be a big factor in flipping the Senate back to Dem control.
All this while various conservative advocacy groups (apparently with a great deal of political pressure) are telling McConnell forget the Senate, we want the Supremes. We're willing to sacrifice the Senate to maintain our hold on the high court. Besides, the Senate hasn't been doing anything for us anyway, at least not on our big issues of abortion and gun rights.
Naturally, McConnell is using this tension to raise a lot of money. And part of that tension is if McConnell does the bidding of these groups he'll likely lose his job of Majority Leader.
Yes, this tactic is based on the assumption the next president will not be named Sanders or Clinton.