Cameron gave his support to Abraham Lincoln, and became his Secretary of War. He only served a year before resigning amidst corruption. Cameron became the minister to Russia during the Civil War, but was overseas for less than a year. He again served in the Senate, eventually being succeeded by his son, J. Donald Cameron, and only resigned from the Senate upon confirmation that his son would succeed him. Cameron built a powerful state party machine that would dominate Pennsylvania politics long after his death.
Cameron was nominated for President, but gave his support to Abraham Lincoln at the 1860 Republican National Convention. Lincoln, as part of a political bargain, named Cameron Secretary of War. Because of allegations of corruption, however, he was forced to resign early in 1862. His corruption was so notorious that a Pennsylvania congressman, Thaddeus Stevens, when discussing Cameron's honesty with Lincoln, told Lincoln that "I don't think that he would steal a red hot stove." When Cameron demanded Stevens retract this statement, Stevens told Lincoln "I believe I told you he would not steal a red-hot stove. I will now take that back." Cameron was succeeded as Secretary of War by Edwin M. Stanton, who had been serving as a legal advisor to the War Secretary. Cameron then served as Minister to Russia.
Cameron made a political comeback after the Civil War, building a powerful state party machine that would dominate Pennsylvania politics for the next seventy years. In 1866, Cameron was again elected to the Senate. Cameron convinced his close friend Ulysses S. Grant to appoint his son, James Donald Cameron, as Secretary of War in 1876. Later that year, Cameron helped Rutherford B. Hayes win the Republican nomination in 1876. Cameron resigned from the Senate in 1877 after assuring that his son would be the successor to his seat. Though Cameron had intended for his son to succeed him as head of the state machine, Matthew Quay ultimately succeeded Cameron as the party boss.
"An honest politician is one who, when he is bought, will stay bought."
"I am tired of all this sort of thing called science here... We have spent millions in that sort of thing for the last few years, and it is time it should be stopped." (on the Smithsonian Institution, 1861)