The Republicans have it fully within their grasp to prevent any Obama nominee from becoming the next Supreme Court Justice–and at the same time to show their base that electing them to office wasn't in vain.
Charles Krauthammer explains why one man–Senate Majority Leader Mitch McConnell–has it in his hands to keep the Supreme Court from receiving in the wanning days of the Obama presidency a new justice who would likely radically alter the balance on the high court:
As I said, this is all about raw power. When the Democrats had it, they used it. The Republicans are today wholly justified in saying they will not allow this outgoing president to overturn the balance of the Supreme Court. The matter should be decided by the coming election. Does anyone doubt that Democrats would be saying exactly that if the circumstances were reversed?
Which makes this Senate majority leader Mitch McConnell’s moment. He and his cohorts have taken a lot of abuse from “anti-establishment” candidates and media for not using their congressional majorities to repeal Obamacare, defund Planned Parenthood, block executive orders, etc. What was the 2014 election about, they say? We won and got nothing. We were lied to and betrayed by a corrupt leadership beholden to the “Washington cartel.”
As it happens, under our Madisonian Constitution, the opposition party cannot govern without the acquiescence of the president, which it will not get, or a two-thirds majority of the Congress, which it does not have.
But no matter. Things are different now. Appointing a Supreme Court justice is a two-key operation. The president proposes, the Senate disposes. There is no reason McConnell cannot hold the line. And he must. The stakes here — a radical generation-long reversal of direction of the Supreme Court — are the highest this Senate will ever face.
If McConnell succeeds, he will have resoundingly answered the “what did we get for 2014?” question. Imagine if the Senate were now in Democratic hands. What we got in 2014 was the power to hold on to Scalia’s seat and to the Court’s conservative majority.
Krauthammer notes that the ability to delay the appointment of a new justice will be meaningless if the Republicans lose this year's presidential election. So far, they are campaigning in a manner that increases the likelihood of a loss.