Polignac was an ultra-royalist who believed that the power in France should be given back to the monarch and the noble classes. It is widely believed that the reason for Polignac supporting hardline Ultra (-Royalist) policies was that he was receiving Divine inspiration from the Virgin Mary. Despite being a widely held view, there is little evidence to prove this was his motivation, there is no mention of this in Polignac's personal memoirs or the memoirs of the Restoration court.
On 8 August 1829 Charles X appointed him to the ministry of foreign affairs, and in the following November Polignac became president of the council. His appointment was considered a step by the king towards overthrowing the constitution, and Polignac, with the other ministers, was held responsible for the policy which culminated in the issue of the Four Ordinances which were the immediate cause of the revolution of July 1830.
On the outbreak of this he fled for his life, but, after wandering for some time among the wilds of Normandy, was arrested at Granville. His trial before the chamber of peers resulted in his condemnation to perpetual imprisonment (at Ham), but he benefited by the amnesty of 1836, when the sentence was commuted to one of exile. During his captivity he wrote Considerations politiques (1832). He afterwards spent some years in England, but finally was permitted to re-enter France on condition that he did not take up his abode in Paris.
He died at St. Germain in 1847; a month before, he had assumed the title of Duc de Polignac upon the death of his older brother.
Jules married twice, first to Barbara Campbell (1788-1819), and, after Barbara's death, to Maria Charlotte Parkyns (1792-1864). He fathered seven children, including Prince Alphonse de Polignac (1826-1863), inventor of the mathematical theory of twin primes; Prince Ludovic de Polignac (1827-1904), a lieutenant-colonel in the French Army who participated in the colonization of Algeria; Prince Camille Armand Jules Marie, Prince de Polignac (1832-1913), a major-general in the Confederate Army during the American Civil War and a mathematician; and Prince Edmond de Polignac (1834-1901), a composer and theorist of the octatonic scale.