Maybe it was the serif. Or the lay-out. Campaign posters are not for people to gaze at, examine and brood over. These are not art pieces meant to enhance bare corners. Campaign posters are meant to scream and grab attention.
Saturation is the key.
I noticed that some of the choicest places to post are the concrete islands in the middle of the road. They are slightly below eye level. If you re riding a car or a jeep, you would easily see them. The walls on the side of the road are good for distance viewing for bus riders. There are techniques and strategies for an effective Operation Dikit.