Guinness was elected to the House of Commons in 1865 as a Conservative representative for Dublin City, serving until his death. His party's leader was Lord Derby. Previously he had supported the Liberal Lord Palmerston, but in the 1860s the Liberals proposed higher taxation on drinks such as beer. Before 1865 the Irish Conservative Party did not entirely support British conservative policy, but did so after the Irish Church Act 1869. The government's most notable reform was the Reform Act 1867 that expanded the franchise.