WASHINGTON — President Obama’s health care law remains largely a mystery to most Americans, three years after the president signed it, a new survey shows.

Today, nearly six in 10 Americans say they still don’t have enough information to understand how the Affordable Care Act will affect them.

Ignorance about the law is even higher among Americans who stand to benefit most, with more than two-thirds of people without health insurance reporting they don’t have enough information, the poll from the nonprofit Kaiser Family Foundation found.

Misunderstandings about the law have dogged it since lawmakers debated the legislation in 2009 and 2010, in part because major benefits of the law do not go into effect until next year.

Starting in 2014, insurance companies will be prohibited from denying coverage to people with pre-existing medical conditions and millions of low- and moderate-income Americans will qualify for new subsidies from the federal government to help them buy coverage.

These protections are extremely popular, the Kaiser survey shows, with two-thirds of Americans supporting the new coverage guarantee and more than three-quarters backing the insurance subsidies.

Provisions that close a gap in Medicare drug coverage for seniors and that offer tax credits to small businesses to help them provide coverage to their workers both are backed by more than 80 percent of the public.

A narrow majority of Americans also say that states should accept federal aid to expand their Medicaid programs to cover poor people, an option under the law; 42 percent say states should not exercise this option.

But Americans remain deeply split on the overall legislation with 37 percent saying they have a favorable view and 40 percent saying they view the law unfavorably.

The division reflects a deep partisan divide: Fifty-eight percent of Democrats support it, but just 18 percent of Republicans.