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In page Isabella d'Este:

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After the death of her husband, Isabella ruled Mantua as regent for her son Federico. She began to play an increasingly important role in Italian politics, steadily advancing Mantua's position. She was instrumental in promoting Mantua to a Duchy, which was obtained by wise diplomatic use of her son's marriage contracts. She also succeeded in obtaining a cardinalate for her son Ercole. She further displayed shrewd political acumen in her negotiations with Cesare Borgia, who had dispossessed Guidobaldo da Montefeltro, duke of Urbino, the husband of her sister-in-law and good friend Elisabetta Gonzaga in 1502.[citation needed]