Having been elected M.P. for the Ayr burghs in 1818, he devoted the greater part of his life to the promotion of Liberal reforms. In 1820 he married the only daughter of Sir Samuel Romilly.
The birthplace of Bruce is not certainly known, but was probably Turnberry, his mother's castle on the coast of Ayr.
Feudal law required that the king should take seisin of the earldom before regranting it and receiving the homage, and the sheriff of Ayr was directed to take it on Baliol's behalf.
Shortly afterwards Bruce appears again to have sided with his countrymen; Annandale was wasted, while he, as Walter of Hemingford says, "when he heard of the king's coming, fled from his face and burnt the castle of Ayr which he held."