His father died in June 1675 in Turin at the age of forty after a series of convulsive fevers. His mother was declared Regent of Savoy and, known as "Madame Royale" at court, took power. In 1677, during her regency, she tried to arrange a marriage between Victor Amadeus and his first cousin Infanta Isabel Luísa of Portugal, the presumptive heiress of her father, Peter II and Victor Amadeus' aunt. His mother urged him to agree to the marriage, as this would have left Marie Jeanne permanently in control of the Duchy of Savoy as Regent because her son would have had to live in Portugal with his new wife. The duchy would then revert to the Kingdom of Portugal at her death. Victor Amadeus refused, and a party was even formed which refused to recognise his leaving Savoy. Despite a marriage contract being signed between Portugal and Savoy on 15 May 1679, the marriage between Victor Amadeus and the Infanta came to nothing and was thus cancelled.