The by-election was triggered by the death of the town's Liberal Member of Parliament (MP) Sir Wilfrid Lawson.

At the last General Election in January, the result was; The Liberal candidate chosen to defend the seat was Captain Frederick Guest.

Thirty-one-year-old Guest was a former Conservative who had followed his cousin Winston Churchill, for whom he worked as private secretary, into the Liberal Party in 1904 in support of the policy of Free trade.

The Conservative candidate was Sir John Randles, who had held the seat from 1900 until losing narrowly in the general election in January.

Frederick Guest was eventually returned as a Member of Parliament for East Dorset in the January 1910 general election.