(By Adam Nagourney, New York Times) President Obama is stepping up efforts to maintain public support for his agenda as rising unemployment presents him with the biggest test of his political strength since taking office.Faced with an economic downturn that has proved deeper than the White House initially projected, Obama asked Americans on Saturday to remain patient, arguing that his $787 billion stimulus plan had saved the economy from collapse and put it on a gradual course to recovery.“As a result of the swift and aggressive action we took in the first few months of this year, we've been able to pull our financial system and our economy back from the brink,” he said, deflecting calls for a new round of stimulus spending and saying that his plan was intended to work not in a few months but over two years.Facing an array of challenges on Capitol Hill and concern about the huge budget deficit, he cast his main legislative initiatives, starting with his call for overhauling the health care system, as part of a long-term plan to rebuild the economy on a sounder foundation.Obama returns to Washington today from a weeklong trip abroad at a time when Democrats have grown increasingly jittery about the economy and the political risks of the president's domestic agenda.Aides said Obama's remarks Saturday, delivered in his weekly radio and Internet address, were intended to help regain control of the debate.