A majority of voters say they know little about John F. Kerry's positions on key issues and want the Democratic presidential candidate to detail specific plans for handling the economy, Iraq and the war on terrorism when he addresses the Democratic National Convention and a nationally televised audience on Thursday, according to a new Washington Post-ABC News poll.

The survey suggests that the stakes for Kerry and the Democrats as they began their convention in Boston could not be higher. In barely a month, Kerry has lost ground to President Bush on every top voting issue in this year's election.

A growing proportion of voters say Bush and not Kerry is the candidate who most closely shares their values, and four in 10 believe the Democrat is "too liberal." Bush has even narrowed the gap on which candidate better understands their problems, an area in which Kerry has led.

The poll suggests that negative ads by the Bush-Cheney campaign that have been airing since early March, as well as attacks by Republican officials, have been increasingly successful in planting the image of Kerry as an unreliable leader who flip-flops on the issues -- perceptions that Democrats will work hard to reverse at their convention.

Kerry's advisers down played the results of the Post-ABC poll, asserting that the senator from Massachusetts enters the convention stronger than other recent challengers to incumbent presidents. But they agreed that the four-day gathering in Boston represents a critical opportunity for Kerry to flesh out what is still a partial portrait of his candidacy and said that his chance to communicate directly with voters will pay dividends.

Cheryl Utley, 43, of Lowell, Mich., would seem to be exactly the kind of voter Kerry is targeting this week. Utley, a restaurant worker, is an independent living in a battleground state. She is leaning toward Bush even though she has supported Democrats more often than she has Republicans. "I have more of a sense of where he stands on things than Kerry," she said.

Utley wants Kerry and the Democratic Party to talk about domestic issues, specifically education and "what they plan on doing about health care for middle-income or lower-income people."

"I have to face the fact that I will never be able to have health insurance, the way things are now. And these millionaires don't seem to address that," she said.

The survey found that Kerry and Bush remain virtually deadlocked, with 48 percent of registered voters supporting Bush and 46 percent Kerry. Independent candidate Ralph Nader claims 3 percent of the hypothetical vote. Kerry held a four-point lead over Bush in mid-June and was tied with Bush in a Post survey two weeks ago.

Kerry has slipped even though Bush remains unpopular with many Americans. Currently half of Americans approve of the job he is doing as president and 47 percent disapprove. Fewer than half endorse the way he is managing the economy, the situation in Iraq and health care. More broadly, a majority of Americans -- 53 percent -- say they are dissatisfied with the way things are going in the country, a 21-point increase since Saddam Hussein's government fell to U.S. forces 15 months ago.

Although the electorate remains deeply divided, the survey found one area of broad agreement: Two in three voters say this election is one of the most important of their lives.

"I think it is the most important election since World War II," said Lee Gearhart, 72, a retired insurance agent in Cedar Rapids, Iowa. "It looked like it was a regular election to begin with -- until Mr. Bush got us into war."

The latest Post-ABC survey suggests that voters are impatient to hear from Kerry on key issues in this campaign, presenting Democrats with an opportunity to show their nominee in a favorable light. More than half -- 54 percent -- say they are unfamiliar with Kerry's positions; only one in four is similarly uncertain where Bush stands. Nearly half of all Democrats -- 46 percent -- and a majority of political independents say they are not sure what Kerry stands for.

"I would like him to come right out and explain that to people, what he really believes, in a way that everyone will understand him," said Rose Spalding, 45, a Kerry supporter in Cumberland, Maine. "He needs to be really clear and concise about that and show he's really different from Bush."

At the same time, Kerry needs to show a more human face. "He needs to come down a little bit to be more of an everyday Joe," she said.

In virtually every measure tested, Kerry's image has eroded in recent weeks. He has lost his double-digit advantage as the candidate viewed by voters as more honest and more understanding of their problems. The president also is now seen by voters as the candidate who better reflects their values, and he has increased his advantage as better able to keep the country safe and secure. The proportion of voters who rate Kerry as "too liberal" has increased slightly, from 36 percent in June to 40 percent.

On issues, Kerry has also lost ground to Bush. By increasing margins, the president is seen as better able to deal with Iraq, the war on terrorism and taxes. On two key issues in which Kerry had an advantage as late as two weeks ago -- the economy and education -- the candidates are tied.

Four issues topped the agenda when voters were asked what they most wanted Kerry to talk about in his televised speech from the convention on Thursday: the economy and jobs (20 percent), Iraq (19 percent), terrorism (15 percent), and health care (13 percent).

"You pretty much know what Bush's philosophy is on everything he's doing," said Mike Miller, 57, of Russellville, Ark., who is "on the fence" but favoring Kerry. "I'd like to know about Kerry's philosophy on the economy: how he's going to get our national debt down. . . . Is the deficit even a concern of his?"

"One of the main things I would like to get out of the Kerry and Edwards campaign, especially this week, is a more specific outline of what their real plans are, especially for the war in Iraq," said Morgan Cason, 19, who attends college in Evansville, Ind.

Adam Chen, 45, an engineer living in San Diego is undecided but favoring Kerry. "I don't think the Republicans' policy of tax cuts is going to create more jobs. So Democrats, what are you going to do to create more jobs? They have to answer more questions there."

Tim French, 52, lives in La Plata, Md. He wants to hear Kerry talk about terrorism. "I would like to see Kerry make a definitive statement on what his administration would expect to do in terms of fighting terrorism in the United States. Borders, law enforcement, intelligence: What is he going to be doing that is not being done now?"

A total of 1,202 randomly selected adults were interviewed July 22-25 for the poll, including 974 self-described registered voters. The margin of sampling error is plus or minus 3 percentage points for the overall results and fractionally larger for results based only on voters.

Senior polling analyst Christopher Muste contributed to this report.