© Reuters.

Investing.com - Health insurance stocks bucked the overall market trend Monday, falling as a recent poll of the Democratic field in Iowa showed Sen. Bernie Sanders in the lead.

On Friday, Selzer & Co. released a poll of likely voters in the Iowa caucuses that showed Sanders in the lead at 20%.

Sanders was followed by Sen. Elizabeth Warren at 17%, Pete Buttigieg at 16% and former Vice President Joe Biden at 15%.

Sanders is a harsh critic of private health insurers and is running on a promise to provide a Medicare for All healthcare program.

That would be a “single-payer, national health insurance program to provide everyone in America with comprehensive health care coverage, free at the point of service” with “(n)o networks, no premiums, no deductibles, no copays, no surprise bills,” according to the candidate’s website.

Among the insurers, Cigna (NYSE: ) fell 3.7%, UnitedHealth (NYSE: ) lost 3.1%, Humana (NYSE: ) was down 2.6% and Anthem (NYSE: ) dropped 3.2%.

The iShares U.S. Healthcare ETF (NYSE: ) fell 1.7%.