Timothy Geithner took over as Treasury Secretary in the middle of the greatest financial crisis since the Great Depression. In four years, he helped design the largest government stimulus package in history, and contended with a weak recovery, millions of Americans losing their homes, obstinately high unemployment and complicated budget negotiations. To his fans, he is the figure most responsible for stabilizing the banking system and preventing a catastrophic economic collapse. To his critics, he was excessively generous to bankers and failed to change a system where some banks remained “too big to fail.” In a wide-ranging interview during his last days at Treasury, he kept returning to what has become one of his signature themes—the importance of putting “policy ahead of politics.” All too often, in his view, the best economic policies have enormous up-front political costs. We began by talking about the financial crisis of 2008.