President Barack Obama's Democratic allies in the Senate strove to lock down support to prevail in remaking the US health care system. Adding to their confidence, a wavering Democrat, Senator Ben Nelson of Nebraska, pictured here in October, said he would vote with his party this time but warned he might side with Republicans in subsequent fights.(AFP/Getty Images/File/Chip Somodevilla)AP – Democrats called a revamp of the nation’s health care system long overdue as historic legislation advanced toward a Saturday night Senate showdown, an early test of party unity on President Barack Obama’s top domestic initiative