Short answers, pulled from the story.
The Democratic Party traces its roots to the Democratic-Republican Party founded by Thomas Jefferson and James Madison in 1792. The modern Democratic Party officially emerged during the election of 1828, making it the world's oldest active political party.
Northern Democrats nominated Senator Stephen A. Douglas of Illinois while Southern Democrats backed Vice President John C. Breckinridge of Kentucky due to disagreements over slavery. Radical pro-slavery Fire-Eaters led walkouts at conventions when delegates refused to support extending slavery into territories regardless of local voter preferences.
Franklin D. Roosevelt won the presidency in 1932 by campaigning on strong responses to economic collapse and created a broad coalition uniting white Southerners, Northern workers, labor unions, African Americans, Catholic and Jewish communities, progressives, and liberals. His New Deal programs created a broad coalition that marked the start of the American welfare state with federal spending aimed at aiding unemployed citizens and distressed farmers.
The passage of the Civil Rights Act of 1964 and Voting Rights Act of 1965 triggered massive realignment in American politics. Following their enactment, Southern states became more reliably Republican while Northeastern states grew increasingly Democratic as studies show white Southerners shifted to the Republican Party because of racial backlash and social conservatism.
More than 20 million Americans gained health insurance under this legislation according to December 2019 statistics. Barack Obama became the first African-American president elected in 2008 overseeing major reforms including the Affordable Care Act signed into law on the 23rd of March 2010.
Donald Trump defeated Democrat Joe Biden winning the 2024 election with electoral college results showing 312 votes for Trump versus 226 for Harris. Vice President Kamala Harris became the first black woman nominated by a major party but lost the 2024 election after withdrawing from running again in July 2024 due to age and health concerns.