When Mr. Tilley became lieutenant-governor of the province, he was fifty-five years of age, and he seems to have thought that his political career was ended, because, by the time his term of office expired in its natural course, he would have reached the age of sixty, a period when a man is not likely to make a new entrance into public life. But circumstances, quite apart from any desire on his part, made it almost necessary for him to change his determination, and during the summer of 1878, when the general election was imminent, he found himself pressed by his old political friends to become once more the candidate of his party for his old constituency, the city of St. John. There was great enthusiasm amongst them when it was announced that he would comply with their wishes, and that he had resigned the lieutenant-governorship. The result of that general election is well known. The Liberal party, which had succeeded to the government less than five years before with a large majority in the House of Commons, experienced a severe defeat, and the Hon. Alexander Mackenzie, seeing this, very properly did not await the assembling of parliament, but sent in the resignation of the ministry, and Sir John A. Macdonald was called upon to form a new government. In the cabinet thus constructed Mr. Tilley resumed his old office of minister of finance, and one of his first duties was to assist in the framing of a new customs tariff which was to give effect to the principle, upon which the election had been run, of protection to home industries. This idea of protection had not been heard of in the Canadian confederation as the policy of any political party until Sir John A. Macdonald took it up about a year before the general election, but it proved a winning card and was the means of giving the new government a long lease of power.
Sir Leonard Tilley's speech in introducing the new tariff was well received and made a strong impression upon all who heard it. It was admitted, even by those who were opposed to the views he held, that he showed a great mastery of the details, and that he illustrated in a very clear manner the view that the country was suffering because the duties imposed upon foreign goods were not sufficiently high to protect Canadian manufactures.