From the poll era to the BCS and now the College Football Playoff, repeating as national champions is becoming harder to do now that teams have to fight through a four-team playoff for a trophy. Since the inception of the playoff format in 2014, no team has gone back-to-back, but the LSU Tigers have high hopes to repeat in 2020.
Source: LSU Football: Why the Tigers Will or Won’t Make the College Football Playoff in 2020
LSU Football Report 