In 1768 Maitland stood for Haddington Burghs against Patrick Warrender. There was a double return, but on 14 Nov. the House was informed that Maitland ‘desired not to contest the matter’. In 1774 he was returned against Sir Alexander Gilmour. His parliamentary career is obscure; no speech by him is known; but almost certainly he voted with Administration. From about 1777 he was on active service in America. In May 1778 he commanded a detachment of marines against rebel vessels in the Delaware,1Sandwich Pprs. (Navy Recs. Soc.), ii. 295. and in 1779 served with great gallantry during the campaign in South Carolina. In September 1779 he took part in the defence of Savannah. His leadership until the final repulse on 9 Oct. of the combined French and American forces, inspired the following tribute:2Scots Mag. 1779, pp. 684-5.
The saving the army, the destruction of D’Estaing, the annihilation of the rebel force, and indeed the success of the whole, was owing to his bringing 800 men across the swamps deemed almost impossible, and forcing his way through the enemy troops to join General Prevost ... Great and long fatigue had in the summer impaired the Colonel’s health. During the siege, and at the attack, though his body was feeble the vigour of his mind was unabated; but alas! he lived only two days after the French embarkation.
He died of fever 22 Oct. 1779.