Congress and defeated his Whig opponent, John P. Kennedy, by 500 votes. He was re-elected two years later, and served from March 4, 1847, to March 3, 1851. In Congress, McLane was seen as an exceptional orator, and, during his second term, was chosen as chairman of the Committee on Commerce. He was not a candidate for renomination in 1850. After his tenure in Congress, McLane moved to the Western United States to become a counsel for a mining corporation, which was engaged in legal activities regarding property in California. He remained out West until 1852, when he returned to Maryland to serve as Presidential elector for Franklin Pierce. Ambassador to China and Mexico In 1853, during the Taiping Rebellion, President Pierce appointed McLane as commissioner to China, with the powers of a Minister Plenipotentiary, and at the same time accredited to Japan, Siam, Korea, and Cochin China. Despite the civil war, McLane was ordered to secure commercial relations between China and the United States, and was also ordered to negotiate with the rebels while also retaining diplomatic relations with the Imperial Government. He successfully renewed trade relations between both nations, but returned to the United States in 1854 due to poor health. After his return to the United States, he resumed his political activity by serving as delegate to the Democratic National Convention in 1856, during which he supported future President James Buchanan. The United States and Mexico had broken off diplomatic relations in 1858, after which civil war broke out in Mexico. McLane was appointed Envoy Extraordinary and Minister Plenipotentiary to Mexico on March 7, 1859, and was charged to determine if the government of Benito Juárez, in opposition to the Emperor, was worthy of recognition. He also negotiated, as ambassador, the McLane-Ocampo Treaty, which would have expanded the transit rights of the U.S. across the Isthmus of Tehuantepec to include an interoceanic canal concession. However, the treaty was not ratified by the United States Senate. McLane retired as Ambassador to Mexico on December 22, 1860. American Civil War and return to Congress During the American Civil War, the Federal Government, under President Abraham Lincoln, forcibly forbade the state of Maryland from joining the Confederacy. McLane was a member of the delegation sent to Washington, D.C. to question the actions of the Federal Government. McLane personally believed that the Federal Government did not have the Constitutional right to