Eight congressional Democrats are urging President Barack Obama to suspend the construction of a “border fence” separating the United States from Mexico, a move that is sure to reignite the immigration debate months after the economic crisis bumped the issue from the national stage. The construction of a border fence is a contentious issue in Democratic circles — especially among those congressmen who are of Hispanic decent or represent districts with a large Hispanic presence. They now hope Mr. Obama will undo some of the border-protection policies erected by the Bush administration. And the border fence sits at the top...