Robert F. Kennedy Jr.'s distinctive voice sounds strained, shaky, and raspy due to a rare neurological disorder called spasmodic dysphonia. This condition causes involuntary spasms in the muscles that control the vocal cords, leading to breaks, a strained or strangled quality, and tremulous voice. It is chronic and neurological, affecting the nerves that control muscle movement in the throat, and there is no cure currently. Treatments like Botox injections are used to manage the symptoms. Kennedy has had this disorder for decades, significantly impacting the sound of his voice but not necessarily causing voice fatigue or loss of overall vocal strength.