Critics of Britain's involvement in Iraq urged Prime Minister Tony Blair to step down Saturday after a helicopter crash killed four British soldiers, bringing jubilant Iraqis to the area to celebrate. The ugly confrontation that followed between British troops and Shiite gunmen left five Iraqi civilians dead and was the latest bad news for Blair, whose government has lurched from crisis to crisis in recent weeks. On Thursday, Blair's Labour Party won 26 percent of the vote to the Tories' 40 percent in local council elections. ...[snip] In the latest poll on the war for the Daily Telegraph newspaper, 57...