RUTHFULLY YOURS

Health-care stocks suffered an ugly tumble on Monday, dragging down the overall Dow Jones Industrial Average by nearly 2%. The selloff was particularly marked in biotech, with Nasdaq ’s industry index plunging 6%, extending a 13% drop last week, and erasing all gains so far this year, as the nearby chart shows. Thus does politics injure the real economy.

Analysts attributed the slide to a letter that socialist presidential candidate Bernie Sanders and House Democrats sent Monday to Valeant Pharmaceuticals threatening a subpoena and demanding the drug maker justify price increases for two heart rhythm medications. Valeant shares were off 17% for the day.

The letter illustrates the larger problem of growing political hostility to drug research and development. Last week Hillary Clinton joined the children’s crusade, rebuking “price gouging” and promising to introduce price controls on pharmaceuticals. Enthusiasm for such central planning is rising among Democrats, and even some Republicans, on Capitol Hill.

This political campaign has been dishonest and virtually fact-free, with a focus on list prices that are negotiated down and that the critics know are rarely paid in full. Name-brand prices are rising only modestly after rebates and discounts, and costs over time are rising more slowly than the historical trend.

The critics are quick to latch onto outlier bad actors like the hedge-fund blowhard Martin Shkreli and his 5000% hike for a generic toxoplasmosis medicine. But they rarely reach the root question: namely, value for money and the benefits from the cures and clinical advances that are transforming the treatment of disease and disability at an accelerating pace.

Biotech stock valuations are historically high, so perhaps a correction was overdue. Then again, perhaps investors had been reflecting the fundamentals of a drug-discovery resurgence in which America leads the world. The major risk facing the industry isn’t R&D stagnation or a pipeline that lacks promising therapeutic candidates. The risk is purely political.

Everyone in Washington claims to favor innovation, but in practice that isn’t true. The biotech industry—increasingly crucial to the U.S. economy and public health—is already regulated forwards, backwards and sideways, so even half of Mrs. Clinton’s proposals would do disproportionate damage. The only results will be fewer therapies and less growth, as the markets are starting to recognize.