I can betcha that there are several plots to assasinate the president made by several of the white supremacist groups as we speak or post
It is against the law to conspire against the government, let alone to conspire to assassinate the president.
I'm sure if the agencies such as the FBI or the CIA are tapping the lines under the Patriot Act
there would be more than enough evidence. But would it be a crime if the FBI\CIA knew about such conspiracies and stayed silent or did nothing?