Pummeled by ghastly economic news, President Obama called Monday for more spending and extended tax cuts that he said would help stimulate the economy — but these also could deepen the deficit problems that helped the federal government earn its first-ever debt downgrade last week. The president made the proposals as world stock market indexes were tumbling, and his remarks seemed designed to help the White House regain its political footing by resetting the congressional agenda next month. Mr. Obama said he wants the 2 percent payroll-tax cut extended into next year, the creation of an infrastructure bank by Congress...