After securing the release of her friend Chateauneuf, Mme. de Chevreuse set to work to restore him to his former office of Guard of the Seals, but did not succeed.  She then turned her attention to undermining the power of Mazarin, agitating all emigres returning to France and starting the most outspoken denunciation of the policy of the cardinal, his injustice and tyranny against the nobility.  The cries of disapproval became so general that Mazarin was kept busy warding off the blows aimed at him by his enemy; the latter succeeded in placing Chateauneuf as Chancelier des ordres du roi and in having his estates restored to him, while Alexandre de Campion she placed in the household of the queen.  Mazarin, living in constant dread of her, managed to thwart two of her cherished schemes—­the restoration to the Duke of Vendome of the government of Brittany and the placing of Chateauneuf in the ministry—­upon the success of which depended her own influence and power.

Finding that ruse, flattery, insinuation, and ordinary court intrigues were of no avail, she turned to other methods.  The Importants, a party made up of adventurers and a large number of the nobility, were making themselves felt more and more; they were opposed to Richelieu and Mazarin, and Mme. de Chevreuse became their chief and instigator.  Failing to succeed with the cardinal’s own methods, she decided to assassinate him, but the plot was discovered, the Duke of Beaufort was arrested and all the princes of the party of the Importants were ordered to leave Paris.  Mme. de Chevreuse was compelled to depart from court and retire to Dampierre, and then to Touraine, where she did everything in her power to assist the friends who had compromised themselves for her.  During her first exile she had had the consolation of the friendship of the queen; but now she was banished by the very friend whom she had served so well and who had up to this time been able and willing to afford her comfort and protection.  Through Lord Goring, Count Craft, and the Commander de Jars, she opened up correspondence and negotiations with England, but was again surprised by the vigilant Mazarin and sent to Angouleme; determining to escape, after many hardships, she successfully reached Liege; from there, as head of all foreign intrigues against France, she continued to thwart Mazarin’s foreign policy.

As soon as the first signs of the Fronde broke out, Mme. de Chevreuse became active and succeeded in attracting to her the young Marquis de Laigues with whom, later on, she contracted a mariage de conscience.  As ambassador of the Fronde, she prevailed upon Spain to promise troops and subsidies to her party.  After the peace of 1649, she went to Paris where she found almost all her friends ready to follow her and to pay her homage.  It was she who conceived the idea of an aristocratic league which, under the auspices of the two great princes of the blood, the Duke of Orleans and the Prince of Conde, would unite the best part of the nobility.