A senior Starfleet admiral and Benjamin Sisko's former commanding officer who tried to seize control of Earth under cover of the Changeling threat.
James Leyton was a decorated Starfleet admiral who had once served as Benjamin Sisko's commanding officer aboard the USS Okinawa. By the time of the Dominion threat he held a high position at Starfleet Headquarters, and after a Changeling bombing on Earth he summoned Sisko home to help lead security measures against infiltration.
Leyton persuaded the Federation president to declare a state of emergency, but Sisko discovered that the admiral was secretly orchestrating the crisis. Cadets from an elite Starfleet Academy squad loyal to him had sabotaged Earth's power grid to frighten the government into accepting martial law, which would effectively place Leyton in control of the planet.
Sisko exposed the plan with the help of his crew, and Leyton was forced to back down and resign. The affair showed how the fear of Changeling infiltration could corrode Federation ideals from within, a theme the series returned to with Section 31 and the darker choices of the Dominion War.