His obstruction of Obama judicial nominations forced Senate Majority Leader Harry Reid (D-Nevada) in 2015 to use the 'nuclear option' that changed the requirement of a 60 vote mandate for judicial appointments, but not for The Supreme Court.
This in turn empowered McConnell to use the same tactic for Donald Trump's SCOTUS nominees.
He is revered by many republicans for his refusal to bring President Obama's SCOTUS nominee Merrick Garland up for a confirmation hearing. He later stated, 'One of my proudest moments was when I looked Barack Obama in the eye and I said, 'Mr. President, you will not fill the Supreme Court vacancy.' '