 In interviews, top officials abroad and Democrats said they have witnessed other moments when Biden's behavior concerned them. Some were quickly relieved when Biden appeared to regain his footing. Others were left shaken by the experiences. European officials had already been expressing worries in private about Biden's focus and stamina before Thursday's debate, with some senior diplomats saying they had tracked a noticeable deterioration in the president's faculties in meetings since last summer. There were real doubts about how Biden could successfully manage a second term. But one senior European diplomat said U.S. administration officials in private discussions