Following his term as governor, Powell was elected to the U.S. Senate. Before he could assume office, President James Buchanan dispatched Powell and Major Benjamin McCulloch to Utah to ease tensions with Brigham Young and the Mormons. Powell assumed his Senate seat on his return from Utah, just prior to the election of Abraham Lincoln as president. Powell became an outspoken critic of Lincoln's administration, so much so that the Kentucky General Assembly asked for his resignation and some of his fellow senators tried to have him expelled from the body. Both groups later renounced their actions.