The first major reform of Commons' seats took place under the
Reform Act 1832. The second major reform of Commons' seats occurred in three territory-specific Acts in 1867–68:
The latter United Kingdom set of Acts had fallen short of the
Chartist aim to enfranchise and to equalise the electorates. Electoral quotas diverged and the gap by 1885 widened; most starkly in the retention of boroughs of dubious size and a limited attempt at creation of new urban boroughs. In reductions these previous reforms halved rather merged into their surroundings those boroughs (historic towns) having fewer than 10,000 inhabitants as at the 1861 census.
 In a de-radicalising move a few of largest cities were given three MPs, whereby "no person shall vote for more than two candidates".
 As a result, the net partisan impact of these cities tended to be counterbalanced: for example, a borough formerly represented by two Liberals was now usually represented by two Liberals and one Conservative. In a Commons vote on party lines, the Conservative neutralised one of the Liberals, so that the borough counted for one party-based vote albeit having greater and slightly more equalised non-partisan local issue representation. By contrast the mid-size boroughs with two members such as the new creations — wherever they so happened to have two MPs of the same party — produced twice the voting power in the House as such cities.
By the 1880s, continued industrial growth and resulting population movements had resulted in an increased imbalance between the constituencies in terms of the numbers of MPs and the population.
The Third Reform Bill
William Ewart Gladstone, leading a
Liberal government, introduced a
Representation of the People Bill in 1884, which sought to greatly extend the franchise but not to alter the boundaries of constituencies. The Liberals had a large majority in the
House of Commons, and the measure passed through the House easily. The
House of Lords, on the other hand, was dominated by the
Conservative Party. The Conservative leader,
Lord Salisbury, was opposed to the bill.
 The majority of the Conservative party's MPs were elected by the counties, with the Liberals being electorally strong in the boroughs. He realised that the bill's extension of household suffrage into the counties would enfranchise many rural voters such as coalminers and agricultural labourers who were likely to vote for the Liberals. This, he claimed, would lead to "the absolute effacement of the Conservative Party". Salisbury hoped to use the Conservative majority in the Lords to block the bill and force Gladstone to seek a dissolution of Parliament before the reforms could be enacted. The Lords duly rejected the bill and returned it to the Commons, provoking outrage among the Radical wing of the Liberals. A campaign organised around the slogan "The Peers Against the People" called for reform or abolition of the Lords if they rejected the bill a second time.
The "Arlington Street Compact"
dans October 1884
Queen Victoria intervened in what was rapidly becoming a constitutional crisis, urging the party leaders to meet and break the deadlock. Negotiations duly started at Salisbury's London home in Arlington Street,
Westminster, between the Conservative leader and
Sir Charles Dilke, a member of Gladstone's cabinet. Lord Salisbury agreed to allow the reform bill to pass on condition that a bill to redistribute parliamentary seats was also enacted; the two parties reached an agreement, the "Arlington Street Compact", whereby the bulk of MPs would be elected in single-member constituencies. He calculated that this would minimise the adverse effect on the Conservatives of the extension of the vote: dividing the counties would allow Liberal-voting and Conservative-voting districts to be separated. The division of boroughs would allow the suburban areas of towns to be represented separately from the inner cities, allowing the growth of "Villa Toryism".
 Dilke, a member of the Radical (socially progressive) wing of the Liberal Party, also favoured the division of boroughs to weaken the influence of the Whig faction in the party. Before 1885 many existing two-member boroughs one Whig and one Radical were nominated by agreement, often leading to uncontested elections.