Despite the bad overall numbers, Clinton continues to dominate the early vote:
Of the 34% (272/800) of respondents who said they voted early:
Clinton - 53
Trump - 31
(Derived from "At first glance, the early vote offers a bright spot for Clinton, where she enjoys a 22-point advantage over Trump" and "Among the remaining two-thirds of respondents who haven’t voted but plan to, Trump leads by 21 percentage points, 53-32").
Democrats always destroy Republicans in Iowa during early voting. This is a lower margin for them and less Democrats have voted in Iowa since 2012 so this is quite bad for Clinton.