In October 1753 Thornton was adopted at York as candidate for the forthcoming general election. But a few days afterwards he informed Lord Rockingham that he had decided not to stand, and would give his interest to any candidate favoured by Rockingham. His reasons for declining are not known. Certainly it was not that he did not wish to be in Parliament, for on 13 Apr. 1754 he wrote to the Duke of Bedford (to whom he was unknown) to ask his advice about standing for Westminster.
At the by-election at York in 1758 Thornton stood as Rockingham’s candidate. It was at first expected that he would be returned unopposed, but when it became clear that a contest was probable Thornton’s enthusiasm evaporated. ‘I dread an opposition’, wrote Thomas Place, Rockingham’s agent at York, 6 Nov. 1758,
Thornton did not stand in 1761, and died 10 July 1769.
