One great researcher I worked with told me to always start my searches by brainstorming a list of terms! ("Pencil and paper!" she would say. But I figure typing out my list is okay!)

Maybe you could build that in - a notepad place on the site to brainstorm.

Anyway, if this is designed for 'power users', who do you have in mind? Reporters who follow Congress or state legislatures regularly, or people who cover a million things, including issue that are affected by legislation?