The political consultant Frank Luntz specializes in shaping language to influence public opinion. Through language he aims to attract the listeners’ attention, implant ideas in their memory, and stimulate either positive or negative emotional responses. In his 2007 book, Luntz states that the most effective political rhetoric is characterized by repetition, consistency, simple plain language, catchy memorable phrases, and short sentences. The aesthetic quality of the speeches matter too. A politician’s words should be pleasant to listen to with a rhythmic flow. While the message should be consistent, some degree of novelty is also important to capture the listener’s attention. Moreover, visual images can often have more power than words. While Luntz has been criticized for promoting style over substance (and in effect, manipulation over communication), he states that content is not entirely irrelevant. The speaker must have credibility; if the politician goes too far beyond what is believable, the audience will be turned off.