Who were the "Reagan Democrats?" Why did these Democrats vote for the Republican presidential candidate? 

Reagan defeated Carter by assembling a coalition of Americans who supported business interests, working-class whites opposed to the Democratic Party's support for the minority group interests, evangelical Christians, and conservative Republicans.

Still an opponent of the federal government's policy of ensuring African Americans' civil rights and eager to win the votes of white Southerners, Reagan began his campaign with a rally in Neshoba County, Mississippi, where three civil rights workers had been murdered in the 1960s. In his speech, Reagan did not mention these workers or the civil rights movement. Much of his campaign would be devoted to reducing the power of the federal government and returning more power to the separate states, a position that opponents of civil rights had supported for decades.

White Southerners were not the only voters to be attracted by Reagan's campaign. Long an opponent of the political and cultural movements of the 1960s, Reagan espoused a conservative social agenda, one that appealed to many lower-middle class and working-class white voters. These so-called Reagan Democrats abandoned the Democratic Party, which, they believed, was too devoted not only to the cause of civil rights, but was also committed to welfare, affirmative action, and other social programs that some white Americans also resented. Reagan also proclaimed his opposition to the 1973 Supreme Court decision of Roe v. Wade, which had guaranteed American women the right to obtain an abortion during the first three months of pregnancy. Reagan's candidacy also benefited from the growing power of evangelical Christians, who shared his opposition to abortion. They shared Reagan's belief that American culture had become increasingly secular and immoral since the 1960s. Reagan's most active supporters formed themselves into the New Right, a highly organized network of conservative activism.