Facing an end-of-the-month deadline, the U.S. government is increasing efforts to enroll millions more Americans into Obamacare, including appeals from President Barack Obama and his wife, Michelle. The Obama administration also is developing a strategy to communicate to Americans the penalty for going without insurance after March 31. People without insurance face fines of as much as 1 percent of their income, a penalty that hasn't been mentioned in the government's advertising. About 4 million Americans have so far signed up for private health plans under the 2010 Patient Protection and Affordable Care Act. As many as 3.5 million more have enrolled in Medicaid, according to Avalere Health, a Washington-based consulting firm.