On August 25, the Democratic National Committee changed some national party rules. Superdelegates will no longer be able to vote for president on the first ballot at national presidential conventions. See this story. This is a victory for the Bernie Sanders wing of the party. Because virtually all the superdelegates in 2016 were Hillary Clinton supporters, she enjoyed a big lead in the race for the nomination even before any presidential primaries or caucuses had been held.
The Democratic National Committee also passed rules requiring states that use caucuses to allow absentee voting in those caucuses.