his campaign in the South, as Democrats argued that he worked in unison with Northerners to stop the extension of slavery. In July, Clay wrote two letters in which he attempted to clarify his position on the annexation of Texas, and Democrats attacked his supposedly inconsistent position. Polk narrowly won the election, taking 49.5% of the popular vote and 170 of the 275 electoral votes. Birney won several thousand anti-annexation votes in New York, and his presence in the race may have cost Clay the election. Most of Clay's contemporaries believed that annexation had been the decisive issue in the race, but Polk's savvy campaigning on the tariff may have also been decisive, as he narrowly won pro-tariff Pennsylvania after downplaying his anti-tariff views. After Polk's victory and the final indirect success of Tyler's strategy, Congress approved the annexation of Texas, which was signed by Tyler on his last day in office, and Texas gained statehood in late 1845. Polk administration, 1845–1849 After the 1844 election, Clay returned to his career as an attorney. Though he was no longer a member of Congress, he remained closely interested in national politics. In 1846, the Mexican–American War broke out after American and Mexican forces clashed at the disputed border region between Mexico and Texas. Initially, Clay did not publicly oppose the war, but privately he saw it as an immoral war that risked producing "some military chieftain who will conquer us all." He suffered a personal blow in 1847 when his son, Henry Clay Jr., died at the Battle of Buena Vista. In November 1847, Clay re-emerged on the political scene with a speech that was harshly critical of the Mexican–American War and President Polk. He attacked Polk for fomenting the conflict with Mexico and urged the rejection of any treaty that added new slave territory to the United States. Months after the speech, the Senate ratified the Treaty of Guadalupe Hidalgo, in which Mexico ceded hundreds of thousands of square miles of territory known as the Mexican Cession. By 1847, General Zachary Taylor, who commanded the American forces at Buena Vista, had emerged as a contender for the Whig nomination in the 1848 presidential election. Despite Taylor's largely unknown political views, many Whigs believed he was the party's strongest possible candidate due to his martial accomplishments in the Mexican–American War. One of Clay's most trusted allies and advisers, John J. Crittenden,