1900–1930

Agrarian Democrats demanding Free Silver overthrew the Bourbon Democrats in 1896 and nominated William Jennings Bryan for the presidency (a nomination repeated by Democrats in 1900 and 1908). Bryan waged a vigorous campaign attacking Eastern moneyed interests, but he lost to the Republican William McKinley. The Democrats took control of the House in 1910 and elected Woodrow Wilson as president in 1912 and 1916. Wilson effectively led Congress to put to rest the issues of tariffs, money, and antitrust, which had dominated politics for 40 years, with new progressive laws.

1930–1960

Franklin D. Roosevelt, 32nd President of the United States (1933–1945).

The Great Depression in 1929 that occurred under Republican President Herbert Hoover and the Republican Congress set the stage for a more liberal government; the Democrats controlled the House of Representatives nearly uninterrupted from 1930 until 1994 and won most presidential elections until 1968. Franklin D. Roosevelt, elected to the presidency in 1932, came forth with government programs called the New Deal. New Deal liberalism meant the regulation of business (especially finance and banking) and the promotion of labor unions, as well as federal spending to aid to the unemployed, help distressed farmers, and undertake large-scale public works projects. It marked the start of the American welfare state.^[25] The opponents, who stressed opposition to unions, support for business, and low taxes, started calling themselves "conservatives".^[26]
Until the 1980s, the Democratic Party was a coalition of two parties divided by the Mason–Dixon line: liberal Democrats in the North and culturally conservative voters in the South, who though benefitting from many of the New Deal public works projects, opposed increasing Civil Rights initiatives advocated by Northeastern liberals. The polarization grew stronger after Roosevelt died. Southern Democrats formed a key part of the bipartisan conservative coalition in an alliance with most of the Midwestern Republicans. The economically activist philosophy of Franklin D. Roosevelt, which has strongly influenced American liberalism, shaped much of the party's economic agenda after 1932. From the 1930s to the mid-1960s, the liberal New Deal coalition usually controlled the Presidency while the conservative coalition usually controlled Congress.^[27]
Issues facing parties and the United States after World War II included the Cold War and the Civil Rights Movement. Republicans attracted conservatives and white Southerners from the Democratic coalition with their use of the Southern strategy and resistance to New Deal and Great Society liberalism. African Americans had traditionally supported the Republican Party because of the anti-slavery policies of Abraham Lincoln and the civil rights policies of his successors, such as Ulysses S. Grant. But they began supporting Democrats following the ascent of the Franklin D. Roosevelt administration, the New Deal, the integration of the military and embrace of proposed civil rights legislation by President Harry Truman in 1947–48, and the postwar Civil Rights movement. The Democratic Party's main base of support shifted to the Northeast, marking a dramatic reversal of history.

1960–1980

John F. Kennedy, 35th President of the United States (1961–1963)

The election of President John F. Kennedy from Massachusetts in 1960 was a partial reflection of this shift. In the campaign, Kennedy attracted a new generation of younger voters. In his agenda dubbed the New Frontier, Kennedy introduced a host of social programs and public works projects, along with enhanced support of the space program, proposing a manned spacecraft trip to the moon by the end of the decade. He pushed for civil rights initiatives and proposed the Civil Rights Act of 1964, but with his assassination in November 1963, was not able to see its passage.

Lyndon B. Johnson, 36th President of the United States (1963–1969)

Kennedy's successor Lyndon B. Johnson was able to persuade the largely conservative congress to pass civil rights bill in 1964 and with a more progressive congress in 1965 passed much of the Great Society, which consisted of an array of social programs designed to help the poor. Kennedy and Johnson's advocacy of civil rights further solidified black support for the Democrats, but had the effect of alienating southern whites, who would eventually gravitate towards the Republican party, particularly after the election of Ronald Reagan to the presidency in 1980. The United States' involvement in the Vietnam War in the 1960s was another divisive issue that further fractured the fault lines of the Democrats' coalition. After Gulf of Tonkin Resolution in 1964, President Johnson committed a large contingency of combat troops to Vietnam, but the escalation failed to drive the Viet Cong from south Vietnam, resulting in an increasing quagmire, which by 1968 had become the subject of widespread anti-war protests in the United States and elsewhere. With increasing casualties and nightly news reports bringing home troubling images from Vietnam, the costly military engagement became increasingly unpopular, alienating many of the kinds of young voters that the Democrats had attracted the early 1960s. The protests that year along with assassinations of Dr. Martin Luther King, Jr. and Democratic presidential candidate Sen. Robert F. Kennedy (younger brother of John F. Kennedy) climaxed in turbulence at the hotly contested Democratic National Convention that summer in Chicago (which, amongst the ensuing turmoil inside and outside of the convention hall, nominated Vice President Hubert Humphrey), in a series of events that proved to mark a significant turning point in the decline of the Democratic party's broad coalition.
Republican presidential nominee Richard Nixon was able to capitalize on the Democrat's confusion that year and won the 1968 election to become the 37th president, and would win again in 1972 against Democratic nominee George McGovern, who like Robert Kennedy reached out to the younger anti-war and counterculture voters, but unlike Kennedy, was not able to appeal to the party's more traditional white working class constituencies. During Nixon's second term, his presidency was rocked by the Watergate scandal, which forced him to resign in 1974, being succeeded by vice president Gerald Ford, who served a brief tenure. Watergate offered the Democrats an opportunity to recoup, and their nominee Jimmy Carter won the 1976 presidential election. With the initial support of evangelical Christian voters in the South, Carter was temporarily able to re-unite the disparate factions within the party, but inflation and the Iran Hostage Crisis of 1979–1980 took their toll, resulting in a landside victory for Republican presidential nominee Ronald Reagan in 1980, which shifted the tectonic plates of the political landscape in favor of the Republicans for years to come.