President Obama's moves to boost the labor movement suffered a setback this week, when the administration was forced to cancel the first federal construction contract in more than a decade requiring union representation of workers. The Department of Labor, citing a "need to evaluate the issues" surrounding the union-friendly bidding process, pulled the plug on the competition for a $35 million contract to build a 160,000-square-foot Job Corps Center in Manchester, N.H., after contractors formally challenged the union mandate.