WASHINGTON - Six months after President Barack Obama signed the landmark health care law, the nation still doesn't really know what's in it.

More than half of Americans mistakenly believe the overhaul will raise taxes for most people this year, an Associated Press poll finds. But that would be true only if most people were devoted to indoor tanning, which got hit with a sales tax.

Many who wanted the health care system to be overhauled don't realize that some provisions they cared about actually did make it in. And about a quarter of supporters don't understand that something hardly anyone wanted didn't make it: They mistakenly say the law will set up panels of bureaucrats to make decisions about people's care - what critics labeled "death panels."

The uncertainty and confusion amount to a dismal verdict for the Obama administration's campaign to win over public opinion. Before the final votes in Congress, Obama personally assured wavering Democrats he'd take the case to the American people after the law passed. But it hasn't worked. And in the final stretch before the midterm elections Republicans are united by their call for repeal.

"I'm insecure about a document that was as big as the health care bill and wonder if anybody understands exactly what's in it," said Diann Kelley, 61, a retiree from Marietta, Ga., who says she's "somewhat opposed" to the law. The AP poll was conducted by Stanford University with the Robert Wood Johnson Foundation.

"The main fear is the cost," explained Kelley. "I'm not sure that we can afford to take on something quite as massive as the health care reform with the economy the way it is."

It's not that Kelley has a negative opinion about everything in the law. The prohibition on health insurance companies denying coverage to people because of pre-existing medical conditions "is really a fine idea," she said.

The poll's questions included a true-or-false quiz on 19 items, some of which are in the law and others not. People were also asked how confident they were about their answers.

For the most part, majorities picked the right answers. But a sizable number also got things wrong. And right or wrong, people were unsure of their answers. Two-thirds or more were uncertain about their responses on eight of nine core provisions of the legislation.

Analysis of the findings indicated a split as far as the impact of accurate knowledge, between Democrats and independents on one side and Republicans on the other.

Accurate knowledge of the law made no difference in overwhelming opposition from Republicans.

Michael Cagnina, 33, a web developer from Powhatan, Va., summed it up: "It just doesn't make me feel comfortable that the government is going to give people free health care but ultimately the government's money is my money."

However, for Democrats and independents, the more accurate knowledge people had of the bill, the more they liked it.

"Among Democrats and independents, the lack of knowledge is suppressing public approval of the bill," said Stanford political science professor Jon Krosnick.