Once the House passed a 90 percent tax on AIG bonuses, a mad rush was on in the Senate. Majority Leader Harry Reid went to the Senate floor to propose a quick vote on similar legislation. A single senator could object, delaying a vote for weeks. But fear of siding with reviled AIG executives prevailed, and no senator stepped forward--until Republican whip Jon Kyl finally did. "I don't believe Congress should rush to pass yet another piece of hastily crafted legislation in this very toxic atmosphere," he said. "Therefore, I object." A vote was put off, the AIG furor abated, and the tax on bonuses is now probably dead.

That was easy. A nervy act by a single senator stopped the scramble to punish AIG. That was two weeks ago. Last week, the decision by Republican senator Arlen Specter to oppose card check legislation was similarly decisive. He relegated that bill, designed to let labor organizers form unions without a secret ballot vote by workers, to the unlikely-to-pass bin. Senate Republicans had worked diligently to produce unanimous opposition to card check. But again, the act of one Republican senator was crucial.

So much for easy victories. Republicans now face the most important test of their opposition to liberal legislation since they blocked President Clinton's health care scheme--HillaryCare--in 1994. This time the task is far greater and the number of Republican senators is fewer (41 now, 44 then). And the only hope is the Senate. House Republicans, lacking the power to filibuster, can't help.

The liberal onslaught comes in four parts: government-run health care, a cap-and-trade carbon tax, a vast array of personal and business tax increases, and government authority to seize financial institutions in addition to banks. This is the liberal dream agenda. If passed, it would do what conservatives fear most. It would make America more like Europe, with growing nanny statism and more reliance on government, considerably less on individuals. Let's look at the four.

Health care. President Obama is fond of saying his plan allows people to choose between the health insurance they get through their employer and a government program currently limited to federal workers. Sounds wonderful, doesn't it? It's not. Rather, it's the path to a single-payer health care system--the kind Obama has said he prefers but isn't actually proposing.

His program would have the distinct advantage of not having to make a profit. So it would always be able to offer greater benefits at lower cost (with taxpayers taking up the slack when it lost money). Businesses would have an incentive to increase co-pays and trim benefits and, in effect, encourage employees to switch plans. And if employer-paid benefits are taxed, as administration officials have suggested, the incentive steering workers to the government program will be irresistible.

"There won't be any private sector [in health insurance]," Senate Republican leader Mitch McConnell says, should government-financed insurance be available to everyone. "It's a fast track to single payer." There's an additional fear. The stimulus bill set aside $1.1 billion to research and compare medical treatments and drugs, raising the prospect that government programs would pay for some treatments and medicines but not others and thus open the door to rationing.

Can ObamaCare be blocked? Republicans may threaten a filibuster and force a compromise. But the odds worsen if Democrats use a procedure known as reconciliation to bar a Republican filibuster and require only 50 votes, plus Vice President Biden's, to pass the health care bill. In that case, Republicans would need to recruit at least 10 Democrats, a tall order.

Reconciliation, normally invoked on tax and spending issues, would turn the Senate into a war zone. Republicans would feel free to exploit any parliamentary tactic at their disposal to delay or impede the legislation, tying up the Senate for weeks, perhaps months.