The principal interest in Co. Kerry was Lord Kenmare - the largest landowner but a Roman Catholic. Lord Landsdowne (Shelburne) and the Herbert interest were other absentee interests not fully exerted, although used from time to time. The Earl of Kerry's interest appears to have been joined with the Crosbies, later Earls of Glandore. The four principal interests were the Crosbies, the Blennerhassets, the Fitzgeralds and the Dennys, and they returned the MPs for most of the century. There were other interests, such as the Batemans and by the 1790s the Mullins, who had been present from the beginning of the century, but had expanded their estates around Burnham. In 1727 a short-lived attempt was made to divide the county between the Crosbies, Dennys and Blennerhassets. The county representation was to be rotated between them and the third participant was to be returned for Ardfert in the case of Crosbie and for Tralee in the case of the other two. Upon the death of one of the original participants his rights were to be transferred to his heir, and 'All the said three persons do earnestly recommend to their respective families the substance of the foregoing friendly agreement.'188 In August 1742 the death of Colonel Arthur Denny without issue dissolved the compact and the ties between him and his brother-in-law, the Earl of Kerry, who then turned to his other brother-in-law, Sir Maurice Crosbie, while the Blennerhassets used the opportunity to try to overturn the Denny interest in Tralee. The boroughs of Ardfert and Tralee were also involved in this compact and its break-up.
Throughout the century Kerry was, despite its apparently orderly pattern of returns, 'harrassed by electioneering divisions': these led not only to broken compacts but to duels, suspected murder and even suicide. In April 1794 Sir Barry Denny died and was succeeded by his son and namesake, then in July John Blennerhassett died aged 24. At the ensuing by-election John Gustavus Crosbie of Tubrid (supported by the Blennerhasset family) and Colonel Henry Arthur Herbert, brother-in-law to Lord Glandore, were both candidates. Crosbie took offence at a remark of Sir Barry Denny, the sitting member, and challenged him to a duel; Sir Barry was shot dead. Then in 1797 Crosbie was killed by a fall from his horse while riding home one night, an incident attributed to the appearance of Sir Barry's ghost or to Denny poison. Meanwhile, Sir Barry's father-in-law, who had undertaken the management of his son-in-law's estate, committed suicide in November 1794,leaving his affairs in disorder. Crosbie Morgell (1488), who sat for the Denny borough of Tralee, was reputed to be a 'not over scrupulous solicitor'. By 1800 it has been calculated that there were at least 15 landowners with rent-rolls of over £9,000, and these would all have benefited from the 1793 Catholic enfranchisement. Nevertheless, Crosbies, Fitzgeralds and Herberts continued to represent the county.189 Its electorate probably rose from about a thousand before 1793 to five thousand in 1815.
Co. Kerry had three boroughs - Ardfert, Dingle and Tralee.