The election was held in the middle of Democratic President Lyndon B. Johnson's second (only full) term, and during the Vietnam War.
This was the first election held after the passage of the Voting Rights Act of 1965, which led to a surge in African-American voter participation.
The GOP made inroads into the South and among blue collar workers, foreshadowing Nixon's Southern strategy and the rise of Reagan Democrats, respectively.
Labor union leaders claimed credit for the widest range of liberal laws since the New Deal era, including the Civil Rights Act of 1964; the Voting Rights Act of 1965; the War on Poverty; aid to cities and education; increased Social Security benefits; and Medicare for the elderly.
According to Alan Draper, the AFL-CIO Committee on Political Action (COPE) was the main electioneering unit of the labor movement.