 In 1877 , McClellan was nominated by the Democrats for Governor of New Jersey , an action that took him by surprise because he had not expressed an interest in the position . He accepted the nomination , was elected , and served a single term from 1878 to 1881 , a tenure marked by careful , conservative executive management and minimal political rancor . The concluding chapter of his political career was his strong support in 1884 for the election of Grover Cleveland . He sought the position of secretary of war in Cleveland 's cabinet , for which he was well qualified , but political rivals from New Jersey were able to block his nomination . 
