Sherman served as an opposition MP for the two and a half years of the 27th Canadian Parliament, under leaders John Diefenbaker, Michael Starr and Robert Stanfield, before losing his seat to high-profile Liberal candidate James Richardson by over 8,000 votes in the 1968 federal election.
On November 15, 1979, Sherman's title was again changed to "Minister of Health", and he retained the position for the remainder of the Lyon government's time in office.
Sherman also served as chairman of the Community Services Committee of cabinet from October 20, 1978 to the resignation of the Lyon government on November 30, 1981.
He served as deputy leader of the provincial Conservatives until he resigned his seat to run for the Canadian House of Commons again in the 1984 federal election.
Earlier in 1984, federal Progressive Conservative leader Brian Mulroney warned Sherman and other Tories that they must support French language rights of minorities outside Quebec to run as PC candidates.
Sherman supported Conservative candidate Raj Joshi in the riding of Winnipeg South Centre in the 2004 federal election.