On a macro level, you are of course right, but "every election" is ambiguous, and the only way I would generally approve of its use would be if it included every local, by, diet, gubernatorial and so on election throughout the country during the entire period. Not having been alive for most of this period, and only having moved to Japan 20+ years after it ended, I am not sure. But the LDP has won "almost every election" since 1989 as well, but has not held, for instance, the governorship of Iwate Prefecture for many years.  (聖やや)