I'm trying to locate a short story I read 30 years ago about a public relations guy who is hired to help the government develop a program to reduce the population. He comes up with several ideas promoting sterility, suicide, etc. but the program works a little too well & things spiral out of control with mass suicides, death-cults & the like. In the end he's left with the last group of people on earth who are counting on him to mate with the last females to repopulate the earth. I remember the last line of the story was:
"I don't have the heart to tell them I'm sterile".
I also remember that the President of the USA now dresses up like Uncle Sam.