BAGHDAD – Iraq cracked down on anti-government protesters who have been occupying key public squares for months, leaving four demonstrators dead Saturday in a country reeling from political turmoil and violence. Security forces set fire to protesters' tents in southern Iraq and reopened public areas in Baghdad just hours after a powerful Shiite cleric dealt a major blow to the movement by withdrawing his support, prompting his followers to leave the encampments. Security forces fired tear gas and live rounds to disperse protesters in an operation to clear two squares in Baghdad, killing one and wounding 44, medical and security officials said.