jkcohen626 said: "I think that the open show pattern is definitely a factor, but it's not an end-all-be-all. When you have a performance as INCREDIBLE and a performer as massively talented as Sharon D. Clarke in Caroline, or Change, it becomes pretty easy to see a pattern being broken."
Agreed, and I think the main difference here is that Clarke is the frontrunner. Yes, it's been all actresses from open shows that have won for the past 30 years now, but almost always, there was no performance from a closed show that was really a threat to the far and away frontrunner that season.
For instance, looking back at the past 10 years, we have 6 actresses nominated from closed shows:
Kelli O'Hara in Bridges (who, while I know lots of people on this board wanted to win, was never at all an actual threat to Jessie Mueller who basically had the Tony in the bag from the moment Beautiful opened)
Mary Bridget Davies in A Night with Janis Joplin (see above; same year as Jessie Mueller)
Carolee Carmello in Scandalous (never a threat; the nomination was basically a way to recognize that show)
Laura Osnes in Bonnie and Clyde (same as Carmello)
Stephanie J. Block in Edwin Drood (maybe the closest thing to a real contender, but Patina Miller was still the far and away favorite that year)
Jan Maxwell in Follies (again, a lot of love for her performance, but Audra had that in the bag from the moment Porgy opened)
So while the closed stat is definitely something to note, I think this is a very different scenario than we've seen recently. Clarke is still giving by far the most acclaimed performance of the season, so she certainly seems to have a great chance to break this streak.