Almost every business in the country is feeling buffeted by the recession, but for health insurance companies the bleak economy is only part of the problem. The changing of the guard in Washington is an equal if not more dangerous threat, and together these forces could deal a body blow to a business model that was already teetering. Health plans are losing millions of members who say they can no longer afford their products. Some big employers are becoming increasingly frustrated about how much they spend on health benefits. Smaller ones are being crushed by ever-rising healthcare costs. In addition, the Republicans who pushed to expand the role of private players in the healthcare system have largely been replaced by Democrats who want to overhaul it.