From Longman Dictionary of Contemporary Englishwin/lose by a whiskerwin/lose by a whiskerinformalLITTLE/NOT MUCH to win or lose by a very small amount Schmidt finished second, losing by a whisker in the final event. → whisker
Examples from the Corpus
win/lose by a whisker• Davidson won the election by a whisker.• He finished second in the 1988 Superstars, losing by a whisker in the final event.• In a race that was ultimately won by a whisker, the Powell effect may even have made the difference for Bush. 