Even the Washington Post points out that Hillary Clinton’s call today for 20 days of early voting will not help turnout. As they wrote:
The rationale behind this seems immediately obvious: more time to vote means more voters, and more voters means Democrats do better. Right?
Well, no. Not so far.
A study released in 2013 found that early voting -- absent other changes -- actually lowered the likelihood of voting. Pew Research wrote about the study, explaining one reason why turnout might drop: the amount of effort by campaigns placed on turning people out to the polls appears to drop, given the reduced urgency.
Data from the United States Election Project shows that there really wasn't a consistent link between changes in early voting percentages (horizontal axis) and changes in overall turnout for the highest contest on the ballot (vertical axis) between the 2010 and 2014 midterms or the 2008 and 2012 presidential elections.
The Post goes on to guess at the reasons for Hillary Clinton to advocate something that does not help and may even hurt turnout. Their guesses are awful. However, the fact remains that even the liberal Post admits that early voting does not help, and may hurt, turnout.