President Obama urged reluctant lawmakers Saturday to quickly approve nearly $50 billion in emergency aid to state and local governments, saying the money is needed to avoid "massive layoffs of teachers, police and firefighters" and to support the still-fragile economic recovery. In a letter to congressional leaders, Obama defended last year's huge economic stimulus package, saying it helped break the economy's freefall, but argued that more spending is urgent and unavoidable. "We must take these emergency measures," he wrote in an appeal aimed primarily at members of his own party. The letter comes as rising concern about the national debt...