In 1818 Chaplin, who had previously sat for Stamford as the nominee of Lord Exeter, successfully contested his native Lincolnshire, which his father had represented from 1802 until his death in 1816. At the 1820 general election he offered again as a supporter of the Liverpool ministry. Rumours of an opposition came to nothing and according to Drakard’s Stamford News, the Whig Member Anderson Pelham was proposed and seconded by two of Chaplin’s friends, a ‘political anomaly beyond our sagacity to account’. At the declaration Chaplin applauded ministers for checking the ‘daring spirit of insubordination’ and defended the Six Acts by arguing that no ‘loyal freeholder’ would ever fall foul of them. He spoke of the need for agricultural protection, but not at the expense of ‘other classes of society’.
At the 1826 general election Chaplin offered again for Lincolnshire. On the hustings he declared himself appalled by the consequences of the commercial panic in the winter of 1825-6 and wished tax reductions could have been larger. He denounced William Jacob’s† report to the board of trade on European grain stocks and underlined the need for protection. As to the ‘abstruse and difficult’ currency question, ‘I do not understand it; and I do not believe that anybody in the last House of Commons did’. He supported the abolition of slavery but deplored ‘ignorant meddling’, which would ruin the planters. In response to Johnson’s cross-examination, he declared his readiness to vote for abolition of the malt tax, but refused to be pledged on any other question and bullied by the county’s ‘independent committee’. He denied that he was a bigot on Catholic relief, asserting that the Irish problem was not a religious one, but the result of unemployment and the ‘evils’ of that country’s civil establishment. He remained opposed to parliamentary reform, though he would never condone a corrupt borough. He was returned unopposed.
He voted against Catholic relief, 6 Mar. 1827. He argued against weekly corn averages, which would throw the agricultural market into the ‘hands of speculators’, 19 Mar., and paired against revision of the corn laws, 2 Apr.
At the 1830 general election he offered again, but came under fire from the independents, who tried to get up an opposition. On the hustings Richard Healy of Laughton, one of their leaders, attacked him for his failure to vote for either repeal of the malt tax or protection for wool growers. In reply Chaplin, who claimed that he had gone to London specifically to vote for abolition of the tax, argued that the case for repeal as a measure of relief had been exaggerated. When he found government reducing taxation by £3,500,000 ‘he would not oppose them’ or be a party to the ruin of fundholders. He defended the revised corn laws and the prohibition of small notes, but said he would have no truck with ‘wild and visionary schemes of reform’. He was returned unopposed, dismissing the independents’ attack as a ‘run at my pocket’.
Thereafter Chaplin, who took an active interest in the progress of the Fordingham drainage bill in the Lords and regularly corresponded with Gilbert John Heathcote* and his successor as county Member Charles Anderson Pelham, continued to exercise political influence on the strength of his landed estates.