WASHINGTON (AP) — Joe Biden has won the Democratic presidential primaries of Florida and Illinois. Tuesday’s results show the former vice president building on a remarkable surge as he barrels toward the nomination at a time when the nation is gripped by concern about the new coronavirus. Biden’s victory was another blow to Bernie Sanders, whose early strength has evaporated as African Americans and working-class whites have sided with Biden. But Tuesday’s primaries demonstrated the uncertainty confronting the Democratic contest as it collides with efforts to slow the spread of the virus. Polls were shuttered in Ohio even as voting moved forward in Florida, Illinois and Arizona.