Fiction about a U.S. Presidential candidate

I wonder if someone can remember the title of a book or perhaps it was a short story...I believe from the '60's or '70's?

In the book a presidential candidate was selected by his party to run because he most nearly 'satisfied' the demographics of the voting American public...the title involved a number (the presumed number of discreet demographic groups) e.g., "The 387" or "The 287"

I'd like to relocate this book for reference purposes. My memory is that the fiction of that time is analagous to the 'reality' of this election which I take to be a study in bipartisan mediocrity.

Any help on the title?

BK