I think that the Barack Obama 'Hope' poster is a good example of a successful promotional poster because it is easily recognisable and has lots of imitations across the internet.
The image is of Barack Obama in a stylized stencil portrait theme featuring the colours blue, red and beige - blue and red being 2 of the colours in the American flag.
The poster is by Shepard Fairley and it spread like wildfire during the 2008 presidential campaign. My main thoughts of this poster is of how effective the text is. There was several versions of the poster which similar words such as 'Change' and 'Progress'
I also think the art style is effective because it is unique for a political poster.