President Obama offered an impassioned defense of the Affordable Care Act on Monday, acknowledging the technical failures of the HealthCare.gov Web site, but providing little new information about the problems with the online portal or the efforts by government contractors to fix it. With Republican critics seizing on the Web site’s issues as evidence of deeper flaws in the health care law, Mr. Obama sought to deflect attention from the continuing problems by focusing on ways to get coverage without going online. Like a TV pitchman, the president urged viewers to call the government’s toll-free number for health insurance, acknowledging...