Randolph was born in 1849 in Blenheim Palace. He was the grandson of the then Duke of Marlborough and the third son of the future duke. He was brought up in the palace, and in 1862 he went to Eton College. Randolph remained there until 1867 when he attended New College, Oxford. He studied law and passed out in 1870.
Randolph was able to get a job as a bank manager at the London and America bank, largely thanks to the intervention of his father. Randolph spent much of his time traveling back and forth from London to New York. He found the job itself very boring, but enjoyed socialising with leading businessmen on both sides of the channel. It was in 1872 he met Leonard Jerome, a wealthy New York financier and father to Jennie Jerome. Randolph and Jennie soon became romantically attached and married in 1873. In 1874 they gave birth to a son, Winston.
In 1874 he was elected conservative mp for Woodstock. He soon became a vocal figure in parliament, even though he was a back bencher and a junior member of parliament. He critised Gladstone as a man who "says far too much, but does far too little". Disraeli offered him a cabinet post as minister of food but Churchill refused. Churchill still led conservative back bench opposition to Gladstone and soon developed his own group of supporters, including Arthur Balfour.
In 1878 the liberals came back into government and Randolph moved onto the front bench as shadow navy minister. Although he had a relatively minor post he was, apart from Disraeli, one of the most vocal conservatives in the house. He, together with his group of by 1878 over 40 MP's, broke more and more away from the traditional Tory heart of the Conservative Party.
In 1881 the conservatives returned to government and Churchill became navy minister for three weeks and then home secretary. He built up a strong relationship with the prince of wales who gave him financial support and political support. He dealt with the Scottish nationalist uprisings in the highlands by sending troops there. In April 1881 Disraeli suddenly died, with no clear successor the conservative party held its first ever leadership election. Churchill challenged Lord Salisbury and Sir Stafford Northcote for the leadership, with no clear winner on the first ballot a second ballot was held, on both ballots there was only a 12-vote difference between the first and last candidate. However, Northcote pulled it out on the third ballot, allowing Salisbury to become leader.
Churchill resigned from the cabinet in protest and led nearly 35% of conservative MP's to sign a decree saying that they would not support any bill put forward by Salisbury, and that they would not support a liberal government, and that they wouldn't become the opposition. Salisbury was regarded as an old Tory (although he was only 51) and that he would lead the conservative party to defeat in the next election.
The Salisbury government found it increasingly more difficult to govern. With the party divided now, almost equally between Churchillites and Tories he resigned after 13 months in office. Gladstone formed a minority liberal government, and Salisbury resigned as conservative leader. A leadership election was held and Churchill won the first ballot over Northcote to become conservative leader.
Churchill instituted a new conservative manifesto, written mainly by him and Joseph Chamberlain, that supported reforms. This removed the liberal claim that they supported the masses and improved conservative prospects of reelection. Churchill opposed Gladstone's amendments to the reform bill brought in by Grey 60 years before along with almost every proposal Gladstone had. In 1884, after great pressure from the conservatives Gladstone held an election. It was a conservative landslide and saw the liberal party lose much of its seats in England, relying on Welsh and Scottish MP's.
Randolph became prime minister and brought in, as promised in his manifesto a new reform bill that created 20 more seats in parliament and reorganised boroughs.