I'm not sure at all that the leaker is from Congress. I'm thinking there's someone in the intelligence apparatus who doesn't agree with the President's claims of unlimited powers.
I'm also not sure I don't agree with someone who's uncomfortable with the idea that the "War on Terror" constitutes a "declaration of war" that's required for "wartime powers". We know that the War on Terror isn't going to be won in a few years, or maybe even a few decades. Are you willing to suspend the constitution for that long?
I support the War on Terror. I'm also comfortable with a system that requires warrants for searches, especially when those warrants easy to get, are practically always approved, and can be obtained up to 15 days after the fact. I know it puts me in the minority here, but I'm a little protective when it comes to my civil liberties, and I think it's OK for the NSA to have to ask for a warrant from FISA before listening in. I'll have to see more evidence that getting a warrant would hamper the President's ability to protect the nation. Thing about freedom is, once it's gone it's hard to get back.
You need more information. Apparently they have gotten thousands of warrants from the FISA court and have encountered some situations that were not anticipated by the law.