The feud between left-wing bloggers and the centrist-leaning Democratic Leadership Council is getting hotter at a time when activists on both sides say party unity is critical to winning back the White House next year. The groups held dueling conferences this month, and the Yearly Kos Convention clearly came out on top. It drew 1,500 liberal activists — including 500 bloggers — and a half-dozen Democratic presidential candidates, led by Sen. Hillary Rodham Clinton. The New York Democrat has been embraced by the DLC as one of its own. The DLC drew 350 elected officials to its conference but was...