Back to the Future II calling the Cubs winning the World Series in 2015 has been a fun joke on their fanbase for many years. The joke might be on us now. The Cubbies are firmly entrenched as the second wild card team. Their closest competition are the Giants who are currently 3.5 games back.
Chicago looked like they were going to hit but they've actually been winning games based on their pitching staff. By FanGraphs WAR metric the Cubs have enjoyed the 5th best pitching staff (3.42 ERA, 3.35 FIP, 14.6 fWAR) in baseball this year. That combines their rotation and bullpen.