“The Marching Morons”, was a written in 1951 by Cyril M. Kornbluth. It is a science fiction novella that was originally published in Galaxy. In 1954, Jack Finney wrote the novel “The Body Snatchers”. It was later made into a movie, “Invasion Of The Body Snatchers” that came out in 1956 and a remake came out in 1978.
If you are not familiar with these works, read the stories and watch the 1956 version of the movie. Here is a link to the pdf version of “The Marching Morons”:http://mysite.du.edu/~treddell/3780/Kornbluth_The-Marching-Morons.pdf