Stewart eventually entered the army like his brothers Edward and William. He served in Egypt, Sweden and the Peninsula. In 1812 he was returned in absentia for the family burghs and listed a Treasury supporter. His military service limited his attendance, as anticipated by his brother the 8th Earl, who had suggested to Lord Melville on the eve of Stewart’s election that his brother Edward ‘on the spot’ might be substituted for him, if James’s ‘promotion was secure’.
Stewart did not figure in debate and there is no evidence of independent behaviour but for his votes for Catholic relief, 30 May 1815 and 9 May 1817. He voted with ministers on civil list questions in 1815 and in May 1816; was again on the ministerial side on 17 June 1816, 7 and 17 Feb., and voted for their suspension of habeas corpus, 23 June 1817. In the Parliament of 1818 he presented a constituents’ petition against reform, 6 May, voted against Tierney’s censure motion, 18 May, for the foreign enlistment bill, 10 June, and was still in town supporting ministerial measures against radicalism on 23 Dec. 1819.
Stewart retired from Parliament with a place, and was provided with a succession of others until his death, 18 July 1836.1SRO GD51/1/198/28/17.