I recently found this thread, and it's great to know people who are in the same boat as I am -- the waiting game. To introduce, I'm a graduating senior at Boston, hoping to get into any office, but my top choices were: Public Liaison, Legislative Affairs, and Political Affairs. A classmate of mine also applied for this summer session, so we're just keeping our fingers crossed!
If any words of encouragement, I know that in the Bush era, phone calls were made to screen applicants, but not everyone who was accepted got one. Judging by this rushed process to get the summer session in, it may be up to the department's discretion.
The White House accepts everyone of all ages, with little to a lot of experiences. I've heard of a undergrad freshman getting in to recent grads.
Also, a friend of mine who was a former intern in the Fall 2007 says to definitely try again if this summer falls through. She applied three times before landing the internship, and she recommends applying during the academic year since the summer session is very popular.