James Buchanan (1791 - 1868), the 15th President of the United States of America from 1857 - 1861, circa 1857.
The Leak: In 1848, a correspondent for the New York Herald was arrested for refusing to disclose his source for a leaked draft of a treaty that would end the U.S.-Mexican war. The Senate confined the recalcitrant reporter to a committee room, where he continued to write his columns at double his regular salary. Each night he emerged from captivity to have dinner with the Senate’s sergeant at arms. He never revealed his source, although historical evidence points to Secretary of State James Buchanan as the likely culprit.
The Outcome: The reporter was released after one month of captivity. Buchanan, if he was in fact the leaker, went on to become President of the United States.