Shirley Chisholm, history of diversity and what the h* is a Blue Dog voter?

...Short History of Diversity from ABC News
In 1972, New York Rep. Shirley Chisholm, who was black, launched a largely symbolic campaign for president.
More than a decade later, New York Rep. Geraldine Ferraro was the Democratic vice presidential nominee.
Civil rights activist and Baptist minister Rev. Jesse Jackson won five presidential primaries in 1984 and 11 in 1988. Still, Jackson never secured the nomination.
But this year is different. ... Given that move toward the center, says political consultant Tom Serafin, the Democratic presidential candidates will need to actively court Blue Dog voters, without ignoring the party's more traditional liberal base....