With Sen. Mitch McConnell (R-KY) announcing on Wednesday his intent to end his reign as GOP leader in the Senate, speculation about who will run to replace him in the role quickly began to mount. Top of the list of potential contenders, according to early chatter, appears to be the so-called “three Johns:” Sens. John Thune (R-SD), John Barrasso (R-WY), and John Cornyn (R-TX). Thune is currently the second-ranked Republican in the chamber, serving as minority whip — a role in which the holder performs head counts and rallies members of the party for votes and quorum calls. The No....