Consistent with his nationalist views, Plamondon was a vocal supporter of the Mulroney government's proposed Meech Lake Accord on constitutional reform and opposed Jean Charest's efforts to modify the accord in early 1990. During this period, Plamondon speculated that sovereignty-association between Quebec and Canada would be "logical and reasonable" if the accord failed and added that he might become a "Quebec-only MP" in that event. When the accord was rejected in June 1990, Plamondon resigned from the Progressive Conservative caucus and informed the House of Commons that he could no longer support a united Canada.