SELMA, Ala. – Joe Biden received a warm reception Sunday in this crucible of the civil rights movement as he and other Democratic presidential hopefuls appealed for black support in a town where demonstrators were once beaten for marching for the right to vote. Themes of fighting voter suppression, providing the poor with a way up and defeating President Donald Trump took center stage at events marking the 55th anniversary of “Bloody Sunday,” the day in 1965 white police attacked black marchers in Selma.