Downpatrick was recognised as early as the reign of Henry IV, when letters of protection were granted to the inhabitants. No charter of incorporation is extant, but it returned two MPs to the 1586-7 parliament of Elizabeth I. It was a potwalloping borough with the franchise vested in the £5 householder of at least six months' residence. It had 250 voters in 1784 and 393 in 1818. The returning officer was the seneschal of the manor of Down appointed by the lord of the manor, who in the eighteenth century was the Rt Hon. Edward Southwell (1962) and his descendants (1963, 1964), afterwards Lords de Clifford. They also controlled, at least partly, the borough of Kinsale in Co. Cork.
The Southwells, who were mainly absentees, were usually careful to return either one of their family or a local gentleman. The only challenge to them was that of the Prices, who lived near by at Hollymount. Nicholas Price (1737) had represented Downpatrick in 1692-3 and subsequently sat for Co. Down from 1695 to 1714, and Cromwell Price (1733) had sat for Downpatrick for the entire parliament of George II; his son Cromwell (1734) was persuaded by Lord Downshire to give up all his claims 'whatsoever and forever' in return for a seat for Kinsale at the 1783 general election. In 1790 Lord Downshire was also thought to have his eye on the borough, but boroughs such as this where the patron owned the town were usually secure and, unlike corporation boroughs, recoverable. Despite the previous arrangement in 1791, Lord Downshire unsuccessfully attempted to set up Cromwell Price and Richard Annesley (0048), probably in the hope that their residence - for Co. Down voters tended to be very independent - would count against Lord de Clifford's absenteeism. Lord Downshire even encouraged the repair of the ruined cathedral - the reputed burial place of St Patrick, St Columba and St Brigid - in the hope that this would encourage local esprit de corps, but to no avail. Downpatrick retained one seat at the Union, when the members were Clotworthy (1818) and Josias Rowley (1823) (who lost the Union ballot), relatives of the Southwells.