"The most important fundamental is that 68 percent of American voters have health-insurance coverage they rate good or excellent ... Most of these voters approach the healthcare reform debate fearing that they have more to lose than to gain," pollster Scott Rasmussen wrote recently in the Wall Street Journal.

A prescient political observation is at the core of the Republicans' strategy to defeat the Democrats' bill: focus on the respective parts that voters fear most -- penalty-enforced federal mandates on struggling middle-class individuals and families to buy health insurance that will squeeze their finances; fees on small businesses fighting to survive that do not provide health care; mandates that will raise health-insurance costs on everyone; and the creation of yet another government entitlement program when Medicare, Medicaid and Social Security are nearing the brink of insolvency.

"There is no political downside for Republicans to oppose healthcare bills that will raise insurance premiums, hike taxes, or expand the mountain of federal debt," GOP pollster Whit Ayres wrote this week at the Politico Web site. Ayres' polling finds that "By a margin of 52 percent to 39 percent, voters prefer a plan that 'does not provide health insurance to all Americans but keeps taxes at current levels' over a plan that 'raises taxes in order to provide health insurance to all Americans.'"

Ayres also finds that two of the biggest voting blocs have turned against Obamacare: independent voters who "think far more like Republicans than like Democrats" and seniors, many of whom will lose their popular Medicare Advantage (Medicare plus private insurance) plans.

"Democratic bills target Medicare Advantage for drastic cuts or elimination, which would deny the almost one-quarter of seniors who have chosen Medicare Advantage plans as their preferred option," he says.

If the Democrats succeed in ramrodding their plans into law over fierce public opposition, "they will create an enormous political backlash that will open the door for Republicans to retake control of Congress" in 2010, just as the GOP did after the Hillarycare debacle in 1994, he warned.

This is not an idle GOP political threat. Senate Democrats such as Harry Reid of Nevada, Chris Dodd of Connecticut, Michael Bennet in Colorado and Barbara Boxer of California are running behind in their respective bids to keep their jobs. And races for several open Republican seats are surprisingly tight in Ohio, Missouri and New Hampshire.

There is a lot more riding on Obama's healthcare gamble than just its legislative prospects. There is also the risk of a much weaker Democratic congressional majority in the last two years of his presidency.