Some might say he has yet to grow up.
McConnell: Dems Should 'Grow Up' and Consider Trump Nominees. (The New York Times, 1/8/2017)
Here's what the shameless hypocrite said 8 years ago.
Quote from Feb. 12, 2009, letter to then-Senate Majority Leader Harry Reid (D-NV) from Senator Mitch McConnell (R-KY). [Daily Kos, 1/9/2017)
Original 1/4/2017 post, "Four days into 2017, Mitch McConnel takes huge lead for Hypocrite of the Year"
Quoted in McConnell: Americans Won’t ‘Tolerate’ SCOTUS Blockade. (Morning Consult, 1/4/2017)