Washington ? A senior White House adviser said Sunday the economic stimulus has not yet “broken the back of the recession” but set aside calls for a second massive spending bill. Republicans, meanwhile, called spending under way a failure.

White House adviser David Axelrod urged patience for President Barack Obama’s $787 billion economic stimulus package in the face of sliding poll numbers. Former Massachusetts Gov. Mitt Romney, a past and potentially future presidential candidate, said the spending was ill-designed and served only to expand the size of government.

Republicans have seized on the public’s growing unease over government debt and spending to challenge the popular president. Sensing their own vulnerabilities, Obama’s top advisers have ramped up their defense of spending that is incomplete and going slower than many had hoped.

Some economists and business leaders have called for a second spending bill designed to help the economy through a downturn that has left millions without jobs. Axelrod said it’s too early to know if more spending would be needed or if the administration would seek more money from Congress.