Lord Derby was notable for having begun his political career as a Whig, and, through sympathies with Robert Peel, later becoming a Tory. His Tory government of 1866-68 was responsible for being the one eventually to pass the Second Reform Act, which extended the franchise to some working-class householders. By 1868, however, Derby was nearing the age of 70, and he decided to retire. His place as Prime Minister was taken by Benjamin Disraeli, but at the General Election in 1868, the momentum was now with the Liberals, who won by a majority of 170 seats, making William Gladstone Prime Minister.
Editors. "Derby retires, Disraeli becomes Prime Minister, then loses election". The Literary Encyclopedia. First published 30 August 2013
[http://www.litencyc.com/php/stopics.php?rec=true&UID=1860, accessed 26 March 2017.]