Unlike his brother, who inherited the Bargany fortune, Sir Hew possessed no great wealth, and was chiefly concerned to obtain preferment for himself and his family. He was returned for Haddingtonshire in 1754 under an agreement with Argyll and Lord Milton, by which Dalrymple was to represent the county and Milton’s son, Andrew Fletcher, the burghs. Having failed in 1754 to secure the office of Lord Lyon,
[Drummore] was at the head of what I must call the clan of Dalrymple which was in many respects too similar to a Highland clan ... I hope this is the last in the low country, and if no new head is permitted to rise, the death of Lord Drummore will I hope break that cement.
Sir Hew’s applications were unsuccessful until 1756, when he obtained for himself the reversion of the office of King’s remembrancer,
Under the Pitt-Devonshire Administration, when his brother ‘had much to say with the Grenvilles’, Sir Hew apparently remained loyal to Newcastle on whose side he voted, 2 May 1757, in the Minorca debate. Although claiming that ‘he had sacrificed every other political connexion and private friendship in adhering firm to Argyll’,
When I solicited his Lordship he made no other objection than that your Grace had formerly complained of me ... I flatter myself that misrepresentation is now removed ... by Mr. Stanley. As the president must still look upon me as a person ungrateful to your Grace, I hope you will remove the prejudice by writing to him.
And Newcastle wrote to Dundas, 20 June 1760:
In the new Parliament Dalrymple spoke in the budget debate of 15 Dec. 1761. Harris records:
Sir Hew ... got up and opposed the measure, particularly ... tax on windows ... talked in the old style of taxes on luxury, post chaises, sugar etc ... ’twas a dry debate.
On Newcastle’s going into opposition, Dalrymple deserted him for Bute. Under Grenville’s Administration he hoped for lucrative preferment. When his kinsman John Dalrymple proposed that Sir Hew be appointed a Scottish customs commissioner and transfer his burghs to him, James Stuart Mackenzie replied:
Neither his Majesty nor Mr. Grenville would think Sir Hew’s conduct merited such a mark of favour as to give him who already had the reversion for life of one of the best offices in Scotland ... another good place ... which would put it out of his power to make any return to Government as a parliamentary man.
Although disappointed in his hopes, Dalrymple maintained his friendly relations with Grenville, followed him into opposition, and voted against the repeal of the Stamp Act, 22 Feb. 1766. Under the Chatham Administration he continued his connexion with Grenville, but made approaches to Government through the Bute connexion. In October 1766, ‘under age, infirmities and entanglements’,
He voted with the Opposition on the land tax, 27 Feb. 1767, but in March was counted by Newcastle as an Administration supporter. When in the summer of 1767 Grafton dashed his hopes of Government support in his county election, Dalrymple turned once more to Grenville,
Twenty-seven years in Parliament has pretty well satisfied my curiosity, during which time ... I have been as little troublesome in solicitations and as constant in attendance as any man ... If therefore Lord Bute or the Duke of Grafton want to have any other man ... I am ready to ... support their friend, or if they will accept of my son ... I am willing to make him over to them ... Let Lord Bute name the candidate from among the old friends of the Argathelians, I shall be the agent of his commands.
When Grafton proved obdurate Sir Hew withdrew and gave his interest to Fletcher’s cousin, who was defeated.
In September 1768 he succeeded to the office of King’s remembrancer, which two years later he sold to Andrew Stuart.
