Major writings and political thought
A lifelong Unionist Party (UK) member, Oliver expressed his political leanings in a series of books, pamphlets, and newspaper articles. In one of his first pamphlets, The Statesman and the Bishop, he came out in favour of Imperial Federation, saying that: "… the union of the British race, the firm and effective federation of our people in all quarters of the earth, appears to me to be of such transcendent importance as a matter of both morals and of politics, that if the achievement of it required a sacrifice instead of a gain, I should be prepared to make it.
"The desire for union, the grand Federal Idea, comes first, and a long way first among my motives."
In 1906 Oliver published the biography Alexander Hamilton, which used the example set by the federalists of the early United States to argue for a federal arrangement for the British Empire. The book came to the attention of Lord Alfred Milner and the members of "Milner's Kindergarten," who were then engaged in the reconstruction of South Africa following the Boer War of 1899–1902. According to Leo Amery, a friend of the kindergarten, "Alexander Hamilton became the Bible of the young men of Milner’s Kindergarten." In 1934 The Times asserted, "The book had probably more influence than any other political book of the decade." Novelist John Buchan, another friend of the Kindergarten, believed that Oliver had "a real and enduring influence on political thought."
Oliver's biography of Hamilton was also influential in the United States. Oliver had interpreted the Hamilton–Jefferson rivalry as a conflict between two ideologies and types of statesmanship: the one based on reality, the other duped by illusion; the one commanding, the other led by circumstances; the one nationalist, the other individualistic. Theodore Roosevelt praised the book and sent copies to Henry Cabot Lodge and Whitelaw Reid, and Walter Lippmann hailed it as "one of the noblest biographies in our language". According to Newton D. Baker, Woodrow Wilson also greatly admired the book.
Oliver also wrote numerous political articles for The Times using the pseudonym "Pacificus". These articles, which first appeared in May 1910, outlined his federalist ideas, especially his proposal for the establishment of separate parliaments in the United Kingdom to deal with purely local issues, while a supreme parliament would be responsible for national and Imperial concerns.
Even while advocating the creation of parliaments for Britain and the Empire as a whole, Oliver was deeply critical of British democracy. He expressed these feelings in private, such as a letter he wrote during World War I that said, "…Democracy is not going to win this war or any other – if we win, it will be because the spirit of the small remnant who hate and despise democracy and all its works will save the country in spite of its democratic government." His attitude led him to play a part in the fall of the Asquith government later in the war as a member of the so-called Monday Night Cabal."
