Shortly before succeeding to the title Hillsborough was returned for both Warwick and Huntingdon as an opposition Whig, choosing to sit for Warwick. Taking the lead in the agitation against the Lords’ rejection of the bill indemnifying witnesses against Walpole, he supported a motion declaring this to have been an obstruction to justice, which might prove fatal to the liberties of the country.
At the beginning of the next Parliament Hillsborough was classed as Opposition. However, when Dodington joined the Prince of Wales in 1749 he made no attempt to recruit him. The 2nd Lord Egmont wrote in his electoral survey, c.1749-50:
Lord Hillsborough has strangely and fulsomely declared himself in commendation of this Administration. He seems a man not to be depended upon at all, if to be avoided.
Thenceforth he became a regular government spokesman. In 1751 he moved the address of condolence on the death of the Prince of Wales, spoke on the Regency bill in support of the clause prolonging the sitting Parliament in the event of a demise, and drew up the heads of a bill for a similar prolongation of the Irish Parliament. Writing about that time Horace Walpole describes him as
a young man of great honour and merit, remarkably nice in weighing whatever cause he was to vote in, and excellent at setting off his reasons, if the affair was at all tragic, by a solemnity in his voice and manner that made much impression on his hearers.
In 1752 he is said by Newcastle to have ‘distinguished himself extremely’ on the subsidy treaty with Saxony, speaking ‘very strongly for us and upon right principles’. During the same session he also spoke in support of a bill for granting forfeited estates in Scotland to foreign Protestants, grounding himself on the ‘mountains of Papists settled by Protestants in Ireland’.
Hillsborough defined his political principles in a pamphlet published in 1751, advocating a union between Great Britain and Ireland, in which he suggests that what he calls the ‘unnecessary spirit of opposition’ might be mitigated by the importation into the British Parliament of an element of disengaged and unbiased Irish representatives who
are yet untainted with that unhappy distinction between court and country. I had almost said, that unmeaning distinction. A prince, who knows our constitution, if not irritated by an unnecessary malignant opposition to his measures, and the people, if not inflamed by the bad arts of a few designing ambitious, turbulent spirits, will easily distinguish, and naturally pursue the public good. Their interests are truly inseparable. They should not be supposed capable of being divided, and ought not to be distinguished away by party or by factions. At least it is a contradiction to the principles of patriotism, certainly to those of liberty, to enlist in a party against the court; to think it a breach of engagements ever to imagine it right in its measures, or give a vote in its favour. As if his Majesty were the only person in his dominions, incapable of knowing his own interests, and his ministers were almost infallibly either weak or wicked.
A proposal for uniting the Kingdoms of Great Britian and Ireland (London and Dublin 1751, 2nd ed.), 37-38.
Under George III these principles were to carry him to high political office.
He died 7 Oct. 1793.