Described as having a "jovial manner and perpetual grin", Withers quickly gained a reputation as the Liberal numbers man and served as Senate Government Whip from 1969–71. After the defeat of the McMahon government in 1972, Withers became Opposition Leader in the Senate, where he retained a thin majority and acted to block much of the Whitlam Government's legislation. Withers was widely known as "The Toecutter" for his alleged approach to enforcing party loyalty and his role in the 1975 Australian constitutional crisis.