I previously looked at how the Liberals have fared in past coalitions, but what of the Conservatives? Well the answer is that the Conservatives didn't suffer any long term damaging splits, but did find themselves in governments that not everyone was terribly happy with particularly the right (or "die-hard") wing of the party.
The first major coalition was that of the Conservatives and Liberal Unionists, a group of Liberals who broke away over Gladstone's proposals for Home Rule for Ireland. Although the first appointment of a Liberal Unionist as a minister was at the start of 1887, it was not until 1895 that a ministry fully combining the two was formed. The Unionists governed for ten years and increasingly became a single entity. When they split over proposals for tariff reform there were Conservatives and Liberal Unionists on both sides of the divide. Eventually in 1912 the parties formally merged, long after they had practically done so already.
The next was formed during the First World War when Herbert Asquith formed a multi-party administration in response to criticism of the conduct of the war. The Conservatives did rather badly out of the distribution of offices - there were Liberals as Prime Minister, Chancellor, Home Secretary, Foreign Secretary, Minister of Munitions and more. The Conservative leader was given the Colonial Office and his leading lieutenant the India Office. The one significant office held by a Conservative was the Admiralty. It was not exactly the best share of offices (and not just for the Conservatives - the Labour leader got Education!) and it contributed to the unhappiness that lingered throughout the remainder of Asquith's premiership.
Andrew Bonar Law was persuaded to return to the leadership and become Prime Minister of an independent Conservative government even though he was not in the best of health. Chamberlain and most of the other leading coalition Conservatives were temporarily cast into the political wilderness, but within a couple of years the party was reunified under Law's successor, Stanley Baldwin. There was no substantial breakaway alternative Conservative party that competed at the polls.
Baldwin claimed to dislike coalitions, but the events of 1931 propelled him into another. Perhaps the situation was eased by Lloyd George being ill at the time and thus unable to take part. But what began as an emergency National Government to balance the budget and restore confidence in the currency soon became a permanent entity, holding power until the Second World War. Curiously the government was led for the first four years by Ramsay MacDonald despite his National Labour party having only 13 MPs compared to the Conservatives' 473. But then such an arrangement suited Baldwin. More significantly the National Government proved very willing to take on the die-hard wing of the Conservatives over Indian Home Rule. Over four years the government passed the Government of India Act 1935 despite fierce opposition from the likes of Winston Churchill. The National Government allowed first Baldwin and then Neville Chamberlain to govern more from a more moderately position than a single party Conservative government would have done so. The right of the Conservative party found its influence limited but it had little alternative option than to acquiesce.
The National Government eventually fell in 1940 in the circumstances described in my previous post The Norway Debate. Churchill formed an all party coalition which fought the war until breaking up after the defeat of Germany. For the most part this was the end of coalitionism until this month. But there were two possible additions.
The first was the "caretaker" government Churchill formed in May 1945, combining the Conservatives, Liberal Nationals and various non-party ministers who had been recruited during the war. This government lasted only two months but had the notable success of introducing child allowances. Being composed of nominally multiple parties it was still a coalition, even if the Conservatives and Liberal Nationals would start a formal amalgamation in opposition in 1948. As with the Unionist coalition of an earlier generation the National Government coalition proved the means by which the Conservatives ultimately absorbed a large chunk of the Liberal party.
The other was Churchill's 1951-1955 government. Whilst supported exclusively by the Conservative party it was broader than a single party administration. A number of the wartime "non-party" ministers was once more appointed and there was even an offer to Clement Davies, the leader of the Liberal Party. It may have been a coalition, it may have been a personalist government but it was certainly not a party government.
The Conservative record from coalitions is thus mixed. On the one hand they have been the means by which the party has absorbed recruits from the left and broadened its political base. They have also suffered no significant electoral breakaways or disasters simply from being in a coalition. On the other hand the governments produced have usually been significantly different from the single party Conservative orthodoxy of the relevant generation and key sections of the party have found themselves isolated. Is the pattern being repeated now?