Harry McCalmont Conservative Charles Day Rose Liberal The 1903 Newmarket by-election was a parliamentary by-election held on 2 January 1903 to fill a vacancy in the United Kingdom House of Commons for the Eastern or Newmarket Division of Cambridgeshire.

The vacancy occurred with the sudden death of the sitting Conservative Member of Parliament, Colonel Harry McCalmont on 8 December 1902.

Both candidates were involved in the horse racing industry, the major employer in and around the town of Newmarket.

Rose stated that he strenuously supported Protestant principles and opposed any legislation that would undermine the ascendency of Protestantism.

This satisfied the Association, and was probably responsible for a large number of Evangelical Christian voters switching allegiance from the Conservatives to the Liberals.