There were many ways the DNC and other Democratic Party leadership tipped the scales to help nominate Hillary Clinton in 2016, but the biggest issue in my opinion was the horrendously inadequate debate schedule.
Although the DNC did eventually agree to add four extra debates near the end of the primary season – one of which never occurred – the 2016 schedule was whimpering weaksauce compared to the 2008 schedule. Throughout the 2007-2008 Democratic primary season, there were 20 debates. 20! Additionally, a whopping 12 of them happened before the first-in-the-nation Iowa caucuses. In contrast, throughout the 2015-16 primary season, only nine debates actually occurred, and only four of them happened before the Iowa caucuses.