The election of Andrew Jackson in 1828 was a significant milestone, as Jackson was not part of the Virginia and Massachusetts elite that had held the presidency for its first 40 years. Jacksonian democracy sought to strengthen the presidency at the expense of Congress, while broadening public participation as the nation rapidly expanded westward. However, his successor, Martin Van Buren, became unpopular after the Panic of 1837, and the death of William Henry Harrison and subsequent poor relations between John Tyler and Congress led to further weakening of the office. Including Van Buren, in the 24 years between 1837 and 1861, six presidential terms would be filled by eight different men, with none serving two terms. The Senate played an important role during this period, with the Great Triumvirate of Henry Clay, Daniel Webster, and John C. Calhoun playing key roles in shaping national policy in the 1830s and 1840s until debates over slavery began pulling the nation apart in the 1850s. Abraham Lincoln's leadership during the Civil War has led historians to regard him as one of the nation's greatest presidents. The circumstances of the war and Republican domination of Congress made the office very powerful, and Lincoln's re-election in 1864 was the first time a president had been re-elected since Jackson in 1832. After Lincoln's assassination, his successor Andrew Johnson lost all political support and was nearly removed from office, with Congress remaining powerful during the two-term presidency of Civil War general Ulysses S. Grant. After the end of Reconstruction, Grover Cleveland would eventually become the first Democratic president elected since before the war, running in three consecutive elections (1884, 1888, 1892) and winning twice. In 1900, William McKinley became the first incumbent to win re-election since Grant in 1872. After McKinley's assassination, Theodore Roosevelt became a dominant figure in American politics. Historians believe Roosevelt permanently changed the political system by strengthening the presidency, with some key accomplishments including breaking up trusts, conservationism, labor reforms, making personal character as important as the issues, and hand-picking his successor, William Howard Taft. The following decade, Woodrow Wilson led the nation to victory during World War I, although Wilson's proposal for the League of Nations was rejected by the Senate. Warren Harding, while popular in office, would see his legacy tarnished by scandals, especially Teapot Dome, and Herbert Hoover quickly became very unpopular after failing to alleviate the Great Depression. Imperial