Discounting the entries for "No Vote," (blanks, abstentions, etc.), which shouldn't count toward the number of ballots cast, I checked the percentages of votes with preference, and look at what percentage of the votes it took to win the Hugo Award in 1964:
Novel: Here Gather the Stars (Way Station) by Clifford D. Simak: 24%
Short Fiction: “No Truce with Kings” by Poul Anderson [F&SF Jun 1963]: 37%
Professional Magazine: Analog Science Fiction and Fact ed. by John W. Campbell, Jr.: 34%
Fanzine: Amra ed. by George H. Scithers: 32%
Professional Artist: Ed Emshwiller: 30%
Publisher: Ace: 36%
Or, to put it another way, between roughly two-thirds and three-quarters of all the voters who expressed a preference preferred some other nominee over the one that won in each category.
This to me is why our current Hugo voting system (instant-runoff voting), complex as it is to so many people, is more fair and more likely to return a result that represents a candidate who, if not necessarily best-liked by a majority, is certainly not actively disliked by a majority of the voters. (This says nothing about those people who don't vote, of course.)