The by-election was caused by the resignation of the sitting LiberalMP, George Esslemont for reasons of ill-health. Esslemont had been MP for Aberdeen South since retaining the seat for the Liberals in a by-election in February 1907 following the appointment of James Bryce to be British Ambassador to the United States. Although he was aged only 57 years, Esslemont died on 2 October 1917, just a few months after stepping down from Parliament.
Candidates
Liberals
On 1 March 1917, it was reported that the Liberals intended to put forward the name of Sir James Murray, the former MP for East Aberdeenshire. In fact the local Liberals were in dispute over their candidate, reflecting the growing division in the party between those supporting the coalition government of David Lloyd George and those favouring the opposition Liberals led by H H Asquith. Murray was said to be a strong supporter of Lloyd George's government. The Asquithians gave their backing to Vivian Phillipps, Asquith's private secretary. A third name was also under consideration, that of Sir John Fleming, an ex-Provost of Aberdeen. Fleming may well have been seen as a good compromise candidate, as, following the intervention of the prime minister himself, Murray was persuaded to withdraw from the contest and Fleming was formally selected.
Conservatives
As partners in the wartime coalition government, the Conservatives abided by the electoral truce between the main parties and did not put forward a candidate.
The writ for by-election was issued in Parliament on 26 March 1917. Nomination day was 30 March, with polling to take place on 3 April. Despite the atmosphere of wartime campaigning and the absence of a Tory candidate, some Liberals were fearful of the result. It was reported that there had been a backlash amongst some of Sir James Murray's supporters, who had not accepted his withdrawal and who refused to vote for Fleming; that Watson had the potential to get a large vote from Labour supporters, from Unionists, who had no candidate of their own, and disaffected Liberals.
Result
The result however was a comfortable win for Fleming, with a majority of 1,776 votes over Watson or 34.7% of the poll. This was consistent with other election results in Scotland during the war with public opinion overwhelmingly pro-government. Fleming took his seat in Parliament on 24 April 1917 but only represented his constituency until the 1918 general election. Standing as an Independent Liberal he lost to Frederick Thomson, a Conservative barrister who seems to have been awarded the Coalition Coupon.