President Barack Obama on Friday sacked a controversial proposed regulation tightening health-based standards for smog, bowing to the demands of congressional Republicans and some business leaders. Obama overruled the Environmental Protection Agency and directed administrator Lisa Jackson to withdraw the proposal, in part because of the importance of reducing regulatory burdens and uncertainty for businesses at a time of rampant uncertainty about an unsteady economy. The announcement came shortly after a new government report on private sector employment report showed that businesses essentially added no new jobs last month — and that the jobless rate remained stuck at a historically...