Question: Which American-born British socialite was Montagu Porch's stepdaughter, and Randolph Churchill's wife?

Context articles: Lady Randolph Churchill
The Anglo-Saxon Review
Lord Randolph Churchill (book)
Winston Churchill (1940–2010)
Descendants of Winston Churchill
Pamela Harriman
Kay Halle
Loyalist Anti-Repeal Union
Montagu Porch
Charmian Campbell

Lady Randolph Spencer-Churchill, (née Jennie Jerome; 9 January 1854 – 29 June 1921) was an American-born British socialite, the wife of Lord Randolph Churchill and the mother of British Prime Minister Sir Winston Churchill.
The Anglo-Saxon Review was a quarterly miscellany edited by Lady Randolph Churchill, and published in London by John Lane.
 It was short lived, running from June 1899 to September 1901.
 Churchill's son, Winston Churchill, was one of her devoted advisors during the months preceding publication.
 He suggested that the magazine take as its purpose “to preserve a permanent record of the thoughts and aspirations of our times, which vary as swiftly as light changes on running water, for wiser ages yet unborn.”
Lord Randolph Churchill was a two-part biography written by Winston Churchill of his father, the Victorian politician Lord Randolph Churchill.
 It was first published in 1906.
Winston Spencer-Churchill (10 October 1940 – 2 March 2010), generally known as Winston Churchill, was a British Conservative Party politician and a grandson of former Prime Minister Sir Winston Churchill.
 During the period of his prominence as a public figure, he was normally referred to as Winston Churchill, MP, in order to distinguish him from his grandfather.
 His father Randolph Churchill was also an MP.
Sir Winston Churchill, son of Lord Randolph Churchill and grandson of John Spencer-Churchill, 7th Duke of Marlborough, was Prime Minister of the United Kingdom between 26 October 1951 – 6 April 1955 and 10 May 1940 – 26 July 1945.
 In 1908, Churchill married Clementine Hozier, the daughter of Sir Henry and Lady Blanche Hozier.
 By Clementine, Churchill had five children and ten grandchildren, a number of whom are well known in their own right.
Pamela Beryl Harriman ("née" Digby; 20 March 1920 – 5 February 1997), also known as Pamela Churchill Harriman, was an English-born American socialite who was married and linked to important and powerful men.
 In later life, she became a political activist for the Democratic Party and a diplomat.
 She was married three times, her first husband being Randolph Churchill, the son of prime minister Winston Churchill.
 Her only child, Winston Churchill, was named after his famous grandfather.
Katherine 'Kay' Murphy Halle (1904–1997) was a Cleveland journalist, author, radio broadcaster, department store heiress, World War II intelligence operative with the Office of Strategic Services, and intimate confidant and/or mistress of many luminaries of the 20th century, including George Gershwin, Randolph Churchill, W. Averell Harriman, Joseph P. Kennedy, Walter Lippmann, and Buckminster Fuller.
 She compiled and edited "Irrepressible Churchill: A Treasury of Winston Churchill's Wit" in 1966.
The Loyalist Anti-Repeal Union was an Irish unionist organisation established in 1886 in Ulster.
 It was created by the most influential Protestant groups - landowners, businessmen, churchmen - in opposition to Home Rule for Ireland.
 The movement grew rapidly and was helped along by the support of Conservative Party MP Lord Randolph Churchill who had decided 'to play the Orange card'.
 (Essentially Churchill was trying to use Ulster unionism to weaken Gladstone's Liberal Party, in favour of the Tories .
 Churchill also famously said that the movement would receive support in England, and "Ulster will fight, Ulster will be Right").
Montagu Phippen Porch (1877- November 1964) was Winston Churchill's stepfather, although three years his junior.
 He was born in 1877 in Glastonbury, a parish of Somerset in the United Kingdom.
 He was educated at Magdalene College in Cambridge.
 In 1900 he joined the Imperial Yeomanry, which was a Cavalry regiment of the British Army.
 In 1906 he joined the Colonial Service and served as an officer until 1919, with the majority of his duties served in Africa.
 On June 1, 1918, Porch married Lady Randolph Churchill, mother of Winston Churchill.
 There was quite an age difference here as Porch was 42 and Lady Randolph Churchill (Jennie Jerome) was 64.
 It was Lady Randolph's third marriage and the first for the younger Porch.
 The couple remained married for three years until Lady Randolph Churchill's death in 1921.
Charmian Campbell ("née" Charmian Rachel Montagu Douglas Scott; 18 July 1942 – 5 April 2009) was a British socialite and artist.