UPDATE: Per Jennifer Ruben at the Washington Post, Romney threw the gay spokesman to the sharks:
During the two weeks after Grenell’s hiring was announced the Romney campaign did not put Grenell out to comment on national security matters and did not use him on a press foreign policy conference call. Despite the controversy in new media and in conservative circles, there was no public statement of support for Grenell by the campaign and no supportive social conservatives were enlisted to calm the waters.Wow. From the Washington Post's conservative blogger, Jennifer Ruben:
Richard Grenell hounded from Romney campaign by anti-gay conservatives
By Jennifer Rubin
Richard Grenell, the openly gay spokesman recently hired to sharpen the foreign policy message of Mitt Romney’s presidential campaign, has resigned in the wake of a full-court press by anti-gay conservatives.
Pieces in two conservative publications, the National Review and Daily Caller, reflected the uproar by some social conservatives over the appointment. [UPDATE, 4:30 p.m.: Although Grenell also raised the ire of liberal commentators with now-deleted tweets about certain prominent women, none of the sources I spoke with mentioned the tweets as a factor in his resignation decision.]