Why/How did the Democratic Party lose it's dominance?

[Bo]

As PiT mentioned, the Democrats controlled at least one house of Congress all the time between 1968 and 1992, so Presidential elections are not everything. As for losing 5 out of 6 Presidential elections between 1968 and 1988, it was partly because the New Deal coalition collapsed due to dissatisfaction with civil rights, Vietnam, and the culture wars and partly because Democrats just got unlucky. Democrats ran a poor campaign in 1968 and also due to Vietnam, they lost to Nixon. After Nixon won reelection, Watergate occured and the Democrats receveied another chance to govern in 1976. However, there were a lot of problems facing the country and Carter couldn't solve all of them, so Reagan defeated him in 1980. Due to the good economy, Republicans managed to win in 1984 and 1988 as well.