WASHINGTON (Reuters) – The Obama administration has helped pull the U.S. economy back from the "abyss" with aggressive efforts to spur growth and stabilize financial markets, a top White House adviser said on Monday. Defending policies that Republicans have attacked as ineffective, National Economic Council Director Lawrence Summers argued measures put in place by the administration, including a $787 billion stimulus package, had helped turn back the deepest U.S. recession since the Great Depression. "Thanks largely to the Recovery Act, alongside an aggressive financial stabilization plan and a program to keep responsible homeowners in their homes, we have walked a...