Only a few weeks into this midterm election year, the right-wing political zeppelin is fully inflated with secret cash and is firing malicious falsehoods at supporters of health care reform.

As Carl Hulse of The Times reported recently, Democrats have been staggered by a $20 million advertising blitz produced by Americans for Prosperity, the conservative advocacy group organized and financed by the Koch brothers, billionaire industrialists. The ads take aim at House and Senate candidates for re-election who have supported the health law, and blame them for the hyped-up problems with the law’s rollout that now seem to be the sole plank in this year’s Republican platform.

In one typical example, the group’s ad against Representative Gary Peters of Michigan, a Democrat who is running for an open Senate seat, is full of distortions and lies. It accuses Mr. Peters of lying when he said the law bars cancellations of insurance policies. Mr. Peters happened to be right, as millions of people who once faced losing all insurance after they got sick now appreciate. The 225,000 Michigan residents who the ad said received “cancellation notices” were actually told that they could change to a better policy; they were not told they could no longer have insurance, as the ad implies. And though the ad said health care costs are “skyrocketing,” national spending on health care is now growing at the slowest pace ever recorded, in part because of the reform law.

Democrats intend to counter this campaign with the facts, but few of the candidates have the money to do so now. As a result, the campaign is taking a serious political toll, increasing the chances that Republicans who support a repeal of the law will win back the Senate majority this fall.