A Liberal, he was re-elected in every election in one or another riding until dying in office in 1905. From 1902 to 1905, he was the Minister of Marine and Fisheries. When Joseph-Israel Tarte resigned from the Cabinet as Minister of Public Works in October 1902, Wilfrid Laurier, under pressure from Montréalers, gave Préfontaine the portfolio of Marine and Fisheries and, for the same reason, transferred to it from public works as "the major services relating to navigation."
A Liberal politician was re-elected repeatedly until his death in office in 1905. He served as Minister of Marine and Fisheries from 1902 to 1905, after Joseph-Israel Tarte resigned from the Cabinet as Minister of Public Works. This move was made under pressure from Montréalers, who wanted Préfontaine to take over the portfolio of Marine and Fisheries.