The 1903 South Antrim by-election was held after the sitting Unionist MP William Ellison-Macartney had left the Commons to take up the post of Deputy-Master of the Royal Mint. The Unionists nominated Charles Craig, a first time candidate who defeated a Russellite opponent to win the seat.
Craig held the seat through four subsequent general elections.
References
South Antrim by-election, 1903 Wikipedia(Text) CC BY-SA