Democratic consultant Sean Phillippi wrote an interesting analysis throwing cold water on the view that high turnout of a party primary signals a likelihood of high turnout by that party in the general election.
"Just because strong Primary Election turnout can be used to predict a lower margin of victory in Gubernatorial General Elections does not mean that it causes it, and I strongly believe that there is no causal link," he writes.
Seems logical to me that high turnout primaries would be more a function of how competitive and interesting the primary is than how motivated the primary voters are. In fact the supporters of the primary loser might be less motivated in the general.
"Only one time in the last 20 years have more Democrats voted in a Primary Election than Republicans (by 390k votes no less). That was 2002, which was also the year where Republicans enjoyed their largest victory in a Gubernatorial Election over that same time period," Phillippi notes. "The largest Republican turnout margin in a Primary Election was 2010, which was also the year in which Republicans enjoyed their closest November victory in the last two decades.
Read his full analysis here, but be warned: He uses terms like multiple regression analysis and significance levels that may make your eyes hurt.