The government's economic stimulus spending has already had its biggest impact and probably won't contribute to significant growth next year, a top White House adviser said Thursday. Christina Romer, the chair of President Barack Obama's Council of Economic Advisers, said the initial jolt of the $787 billion stimulus expanded the economy in the second and third quarters of this year. But she said the remaining spending will simply keep the economy from slipping. "By mid-2010," she said, "fiscal stimulus will likely be contributing little to further growth." That assessment underscored the fragility of an economic recovery marked by stubbornly high...