On 29 May 1773 he received the office of Great Clerk (Writer) of Lithuania, a relatively low-ranked position that was seen by some as below the magnates of the Potocki family. He participated in the Partition Sejm of 1773, where he sat on several commissions. Seeing himself in opposition to the king, he refused a seat on the Permanent Council that he was offered in March 1774. The king tried to appease him with the Order of Saint Stanislaus on 14 July that year, but that failed to bring Potocki to his side. Instead, Potocki became, for the next decade and half, one of his chief political critics and opponents; on 1776 he went to Moscow to argue, unsuccessfully, for limiting the power of king and the Russian ambassador, Otto Magnus von Stackelberg. Later that year, his election to the Sejm was disputed, and the king and Stackelberg managed to block his election. In 1778 however, the growing rift between the king and Stackelberg allowed him to take, through political maneuvering, the chairmanship of the Permanent Council Marshal of the Sejm. That year he also became a Knight of the Order of the White Eagle.