ORLEANS — Progressive activists at Netroots Nation in New Orleans this past weekend had a message for the establishment of the Democratic Party: start talking about race or step aside. The marquee annual conference for the left — a key stop for possible presidential candidates since its first meeting in 2006 — made it clear in their program at the outset, that “Democrats must abandon the myth of the white swing voter and invest in the multi-racial, multicultural coalition of voters that make up the majority of our electorate.” But some Democrats are better prepared for this than others. In...