Guicciardini endeavoured to restrain him in the indulgence of his vices, but without avail. He was now wholly devoted to his service. When Clement VII. died, his successor wished him to continue governor of Bologna, but he refused. While the see was vacant, he had yielded to the entreaties of the senators, and remained to prevent popular disturbances. They promised him every assistance to maintain his authority; but his enemies took occasion to display their disrespect. Geronimo Pepoli, and others, who some years before had retired from Bologna in distaste, took this occasion to return, accompanied by armed followers and public bandits. Guicciardini's haughty spirit was in arms against the insult. Among the followers of Pepoli were two outlaws under sentence of death; these he caused to be seized, led to prison, and put to death. Pepoli manifested the utmost indignation, and was only restrained by the authority of the senators from giving public token of his resentment. When the new pope was elected, and another governor appointed, Guicciardini prepared to quit the city. Pepoli threatened to attack him on his departure; but he, undismayed, set out at noon-day, accompanied only by a few attendants on horseback. His road led him past the palace of the Pepoli, nor would he diverge from it on this account, but passed under their windows with a firm and intrepid countenance, and was permitted to pursue his way unmolested. He soon after displayed this energy and firmness of character in a very bad cause. The Florentines, unable any longer to endure the tyranny and vices of duke Alexander, appealed to Charles V., whom they regarded as lord paramount of their state. The emperor summoned Alexander to Naples, where he then was, to answer the charges made against him. He obeyed: but the emperor was so incensed that he began to fear the result, and was on the point of retreating, had not Guicciardini exhorted him to remain. He drew up a defence for him, and by a judicious distribution of bribes, succeeded in obtaining his acquittal; and Florence was again subjected to his yoke. Two years after, Alexander was murdered by Lorenzino de' Medici, who considered that he had a better right to be considered the head of the family. But this act, undertaken without the participation of any accomplice, was not followed by the results that might have been anticipated. Lorenzino, frightened by his very success, fled the city, and his cousin Cosmo was raised to the supreme power, and afterwards named grand duke of Tuscany. Guicciardini assisted materially in his elevation, and hoped to be real chief of the state, while the other held the nominal rank. But Cosmo was of a crafty, cold, and ungrateful disposition, and treated his benefactor with such neglect, that he withdrew himself from public life, and retired to his country seat at Montici, in the neighbourhood of Florence.