Please keep in mind I know I'm being off based here.
Although I want to see Annaleigh Ashford win for her divine comic performance, I'm thinking that Patricia Clarkson might pull an upset for The Elephant Man. It's a beautiful, memorable performance. Lydia Leonard also has a strong chance too.
I'm also thinking that Bill Nighy might pull an upset in the Lead Actor category. Voters obviously seem to love Skylight and it doesn't look as if Mulligan will beat Mirren, so it will be a way to honor the acting in that show (unless voters think Revival will be enough). Nighy is a veteran actor and that might appeal to voters not comfortable going with a newcomer like Sharp. And he's a beloved character actor who doesn't come with the celebrity baggage of someone like Cooper, who still more than proved himself in Elephant Man.
The Curious Incident and Hand to God guys might cancel each other out. Plus I do wonder if some might hold the fact that Sharp has an alternate against him. Also, in terms of stage time, Boyer is off stage for quite a bit of Hand to God (for many minutes it's Geneva Carr's show).
The voters might go for Cooper, but seems to be resisting giving awards to Hollywood stars (plus, it probably didn't help that he cancelled performances so he could attend the DGAs--I mean, the Oscars, that's understandable, but the DGAs????)
Ben Miles might suffer from Mark Rylance comparisons--although he certainly gives a great performance--understated, giving a slow burn performance that grows in power over 6 hours.
