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

[LBJ Revivalist]

From 1933 to 1953, and from 1961-1968, the Democratic Party dominated politics--both in the White House and in the Congress. Yet beginning in 1968, the party's dominance was lost and by the 1991 the Democratic Party seemed to be a perpetually losing party (in terms of the WH). Why did the Democratic Party nearly collapse between 1968 and 1992?

[Associate Justice PiT]

     Factoring in the White House gives a problematic image. If you look at only Congress, the Democrats were very much the dominant party until 1980, when they were undermined by the poor economy & the Iranian hostage crisis.

[Tetro Kornbluth]

Because the Republicans ingeniously made the party a scapegoat for various social changes and groups in America (Blacks, Migrants, Intellectuals, Bohemians...) that large numbers of Americans disapproved of.

[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.