Veteran Dem pollster Mark Mellman says so:
[t]here is no relationship between how candidates perform among any particular group of voters in primaries and how they do with that segment in the general election. In 1992, Bill Clinton lost college-educated voters to Paul Tsongas in the early competitive primaries, but he went on to win that group in November by the largest margin any Democrat ever had. Similarly, John Kerry lost young voters in the competitive primaries in 2004 before going on to win them by a record margin in the general election.
--Michael Crowley