OP, the Yale admissions blog answered a mailbag question this week about individuals applying ED. They said they receive updates from peer schools regarding students who applied ED and were accepted at those schools and they immediately remove them from application consideration. Assuming this is a standard practice, you can try and see if you're Harvard material, but they'll certainly take the liberty of withdrawing your application for you.
I just got a letter from Columbia that reads:
We have been informed by the University of Pennsylvania Law School that you have been admitted there under its binding Early Decision Program, and we applaud you on this accomplishment. As Penn Law's Early Decision Program is binding, we have withdrawn your application to Columbia Law School from further consideration.
Just read your contract. Not meaning to lash out at you, but people on this board seem to have a really difficult time understanding a pretty easy concept. BINDING. Meaning withdraw from all schools. All means all. Not some. All.