The Free Beacon has been helpfully informed on Twitter that the phrase Sen. Barbara Boxer uses, is used in the eponymous 1936 film "Straight from the Shoulder."
According to the McGraw-Hill Dictionary of American Idioms and Phrasal Verbs:
Fig. very direct, without attenuation or embellishment. Okay, I'll give it to you straight from the shoulder. Right straight from the shoulder: clean out your desk; you're through.