I believe that Grimes was Supporting because she wasn't a "name" yet and, as such, was billed below the title. In those days, generally only those billed above the title were eligible for the Lead categories (today producers have the power to petition the Tony committee for category changes that don't reflect the billing). The same thing happened to William Daniels in 1776. The entire cast was billed below the title and was automatically considered Featured, including Daniels who's role was clearly a Lead one. Daniels had his name removed from consideration (he, in effect, rejected his nomination) and the award went to Ron Holgate who played Richard Henry Lee from the same show instead.
"What a story........ everything but the bloodhounds snappin' at her rear end." -- Birdie
[http://margochanning.broadwayworld.com/]
"The Devil Be Hittin' Me" -- Whitney
