We need to admit that the other side is and has been MUCH more effective in dreaming up a simple mantra ("Hope & Change", "Nobody is going to take away your guns", "Demand a Plan!", etc.) and then repeating it ad nauseum with the help of a complicit media until the mantra becomes part of the national discourse.
Unfortunately, coming up with a catchy 3- or 5-word slogan is hard. If it were easy, our side would have a catchy 3- or 5-word slogan by now.