[citation needed] On 15 May 1870, he was appointed minister of foreign affairs in the Ollivier cabinet, and was thus largely, though not entirely, responsible for the bungling of the negotiations between France and Prussia arising out of the candidature of Prince Leopold of Hohenzollern-Sigmaringen for the throne of Spain, which led to the disastrous war of 1870-71.

The famous declaration read by Gramont in the Chamber on 6 July, the "threat with the hand on the sword-hilt," as Bismarck called it, was the joint draft of the whole cabinet; the original draft presented by Gramont was judged to be too "elliptical" in its conclusion and not sufficiently vigorous; the reference to a revival of the empire of Charles V was suggested by Ollivier; the paragraph asserting that France would not allow a foreign power to disturb to her own detriment the actual equilibrium of Europe was inserted by the emperor.

That he reckoned upon the active alliance of Austria was due, according to Ollivier, to the fact that for nine years he had been a persona grata in the aristocratic society of Vienna, where the necessity for revenging the humiliation of 1866 was an article of faith.

[2] It was Gramont who pointed out to the emperor, on the evening of the 12th, the dubious circumstances of the act of renunciation, and on the same night, without informing Ollivier, despatched to Benedetti at Ems the fatal telegram demanding the king of Prussia's guarantee that the candidature would not be revived.

The supreme responsibility for this act must rest with the emperor, "who imposed it by an exercise of personal power on the only one of his ministers who could have lent himself to such a forgetfulness of the safeguards of a parliamentary regime."

As for Gramont, he had "no conception of the exigencies of this regime; he remained an ambassador accustomed to obey the orders of his sovereign; in all good faith he had no idea that this was not correct, and that, himself a parliamentary minister, he had associated himself with an act destructive of the authority of parliament."