The Democratic (party) leaders are saying we have a constitutional crisis because of Trump and the declassification of the documents. Brennan says that they should defy Trump's order and risk being terminated to protect the country.
I think the Democrats are ultimately protecting Obama and Hillary Clinton. I believe we do have a constitutional crisis when you can't trust the FBI, CIA and other government agencies (mostly secret) from doing their jobs in a non-partisan manner. This may well rattle the country.