[2] MacSharry was re-elected to the Dáil at the 1973 general election; however, Fianna Fáil went into opposition as a Fine Gael–Labour Party government came to office.

In Jack Lynch's subsequent front bench reshuffle, MacSharry was appointed Opposition Spokesperson on the Office of Public Works.

Although MacSharry was serving as junior minister to Colley, he was one of the strongest supporters of Haughey and nominated him for the position of party leader.

Agriculture was viewed as a key portfolio in Haughey's new cabinet and MacSharry was regarded as an effective Minister at a time when farm prices were falling.

In the new Fianna Fáil front bench, MacSharry was retained as Spokesperson for Agriculture, but a later reshuffle saw him move to fisheries.

Fianna Fáil returned to government following the February 1982 general election and MacSharry was appointed as Tánaiste and Minister for Finance.

He defended his action by saying that rumours were sweeping the party that he could be "bought" to support efforts to depose Haughey; he claimed he used the equipment to record any attempts made to offer bribes.

The scandal was however primarily focused on the decision by the Minister for Justice, Seán Doherty, to bug the phones of two leading political journalists to discover their anti-Haughey sources.

MacSharry was a secondary but high-profile casualty of the scandal, as the equipment he had used had been supplied by Doherty, who had requested it from Assistant Garda Commissioner Joseph Ainsworth.

One of his sons, Marc MacSharry, has served as a Councillor on Sligo County Council, as a Senator in Seanad Éireann representing the Industrial and Commercial Panel from 2002 to 2016, and as a TD for the constituency of Sligo–Leitrim since 2016.