Lévesque and his party had run in the 1970 and 1973 Quebec elections under a platform of separating Quebec from the rest of Canada. The party failed to win control of Quebec's National Assembly both times – though its share of the vote increased from 23 percent to 30 percent – and Lévesque was defeated both times in the riding he contested. In the 1976 election campaign, he softened his message by promising a referendum (plebiscite) on sovereignty-association rather than outright separation, by which Quebec would have independence in most government functions but share some other ones, such as a common currency, with Canada. On November 15, 1976, Lévesque and the Parti Québécois won control of the provincial government for the first time. The question of sovereignty-association was placed before the voters in the 1980 Quebec referendum. During the campaign, Pierre Trudeau promised that a vote for the "no" side was a vote for reforming Canada. Trudeau advocated the patriation of Canada's Constitution from the United Kingdom. The existing constitutional document, the British North America Act, could only be amended by the United Kingdom Parliament upon a request by the Canadian parliament.