If McConnell lets Schumer walk all over him, the Republicans would lose control of the Senate in 2018 even if their candidates ran every race unopposed. These Washington insiders aren't stupid. They know full well that Trump was elected because people are tired of a government that can't even get simple sh!t done.
Something else to consider is that a lot of business and industry groups are pushing hard to get Gorsuch approved. These are the core of the GOPe's financial supporters.