Stuart had been the Duke of Hamilton’s Member for Lanarkshire until his retirement in 1784. Had he stood at that election he was expected to rally to Pitt’s administration under the influence of the duke and Henry Dundas: his politics were a matter of personal loyalties. He was recalled from his antiquarian researches by his friend and benefactor Sir William Pulteney, to whom he had written from Paris in July 1789 approving the ‘ardent spirit of liberty’ there, to become one of his nominees for Weymouth in 1790. At the same time he declined some ‘very honourable and important’ appointment offered him by Pitt, regretting that ‘neither the mens nor the aetas are now the same’, 31 May 1790. When present, he supported government, though he appears to have been, like his patron, in the minority for relieving the Scots from the penalties of the Test Act, 10 May 1791. A month before he had been balloted to the public revenue committee. On 4 Mar. 1793 he was given leave of absence for bereavement and on 3 Apr. 1797 was a defaulter. He appears to have spoken for the cavalry bill, 2 Nov. 1796, rebuking opposition for their lack of confidence in government’s good intentions.1PRO 30/8/181, ff. 128, 130; CJ, xlviii. 318; lii. 450.
In his Genealogical History of the Stewarts (1798), Stuart concluded that he was heir male of the ancient royal line, a claim that did not go unchallenged: it had no future, as he had no heir male. On 27 Nov. 1799 he suggested to Dundas, as ‘a graceful close’ of all his labours, that financial relief should be offered to the unfortunate Cardinal York, the surviving brother of the Young Pretender.2DNB; Kent AO, Stanhope mss 751/8. He died 18 May 1801.