Campbell was returned on the interest of his brother Lord Cawdor, who since 1804 had been leader of the Blue (Whig) party in the borough of Carmarthen. Cawdor was also eager to obtain naval promotion for him through Thomas Grenville at the Admiralty.
In Parliament, where he made no known speech, Campbell supported the Whigs in and out of power, his brother’s line, voting with them on Brand’s motion, 9 Apr. 1807, against the address, 26 June 1807, and pairing in opposition to the conduct of the Scheldt expedition, 30 Mar. 1810, and in favour of Catholic relief, 24 Apr. 1812, 2 Mar. and 24 May 1813. Clearly his naval duties prevented him from attending regularly after 1807, as did indifferent health. In 1816 he was named as prospective candidate for Pembroke Boroughs on his brother’s interest, but nothing came of this plan.
A familiar of the Prince Regent, he was made a groom of the bedchamber in 1817. When the Regent first proposed this to Lord Liverpool in September 1816 the latter, writing to Bloomfield, 13 Sept., objected that although Campbell was ‘a very respectable man’, his brother had ‘always been in opposition’ and he himself had ‘always voted against government till he vacated his seat’; unless Campbell’s family’s politics had changed, which clearly they had not, it was ‘a serious evil to government, and eventually to his Royal Highness, to pass over friends and to promote enemies’. Liverpool went so far as to record that even while Campbell was in professional command at Deal, ‘his language was opposition language’.
To Cawdor’s relief, the difficulty was at length overcome, but all did not end well: on 23 Jan. 1821, while in command at Portsmouth, Campbell took his own life. His valet found him at 6.50 p.m., ‘lying on the floor, with a pistol at his side’. This event was the more distressing as he was ‘of the most humane and charitable disposition, and of exemplary domestic habits’ and ‘highly esteemed by all the navy’. The coroner returned a verdict of lunacy.
