Intended from youth for a parliamentary career, Pryse Campbell was mentioned as a possible candidate for Inverness-shire as early as December 1746.
In Parliament Pryse was at first regarded merely as an appendage of his father. But he soon showed his independence. While friendly with Fox, Pryse did not share his father’s dislike of Pitt, and voted with him on the Minorca inquiry, 2 May 1757.
Under the Newcastle-Pitt Coalition Pryse Campbell maintained his independence. In February and March 1759 he voted for allowing the free importation of Irish cattle, despite the petitions of his Inverness-shire constituents: on this he differed from his father and the majority of Scots Members, and incurred the displeasure of Argyll. Isolated from his friends, he sought to recommend himself to his kinsman Newcastle, to whom he wrote, 24 June 1759:
A young man is not allowed to think for himself and your Grace may have been told that I am attached to a faction and will blindly follow wherever that leads, and though I have a better opinion of my own sense and honesty it is from my actions your Grace should form yours.
He returned to the Scottish fold over the militia, was a member of the committee nominated to prepare the bill, but is not mentioned as having spoken in the debates.
His cattle bill vote was not, however, forgotten. In February 1761 he learned from his friend Sir Harry Erskine that Argyll had ‘put an absolute negative’ upon him as candidate for Inverness-shire.
He voted with the Opposition on general warrants (6, 15 and 18 Feb. 1764), but was counted by Administration as a friend, and voted with them against the repeal of the cider tax.
Listed ‘pro’ by Rockingham in July 1765, he supported the repeal of the Stamp Act; but on 18 April 1766 voted against Dowdeswell’s proposal for a new window tax.
As Nairnshire would not be represented in the next Parliament, Campbell thought at first of contesting Inverness-shire;
