Democrats gather in Denver this week with worries as well as hopes. It's not just that Barack Obama is locked in a dead heat with John McCain. It's also that he is barely winning - and in some polls actually losing - on the issue that should be his strongest - the economy.

If Obama is going to triumph, he needs to attract the middle-class voters who've watched their jobs, health care, retirement savings and family finances grow less secure. But this will only happen if he sharpens and expands his economic message, without further delay. To do that, he must put three moves into his economic playbook so far mostly lacking.

Move No. 1: Act, Don't React.

Rapid response is too late. On the economy, Obama needs to be the candidate to whom McCain is responding. That means relentlessly linking McCain to the economic disasters of the Bush presidency. More than that, it means showing that McCain has flip-flopped to embrace the hard-line policies that got us into our present mess, from runaway deregulation of financial markets to failure to address fundamental problems like health insecurity.

Forget about whether McCain is "fiscally responsible." Go after his soft underbelly - massive tax cuts for the rich to be paid for by everyone else and a risky proposal to tax health benefits and push people out of employment-based coverage into the Wild West of unregulated individual insurance.

Move No. 2: Don't Forget Health Care.

Speaking of health care, where did it go? Last year, Obama outlined a health plan light years better than McCain's - and then pretty much stopped talking about it.

In 1992, James Carville reminded Bill Clinton "Don't Forget Health Care." He knew what the polls show today - people see the economy and health care as intertwined, and Democrats gain when health care is an issue.

Yet during the Olympics, an Obama ad ticked off six economic priorities: "grow the economy," "end tax breaks for companies that ship jobs overseas," "help businesses that create jobs here," "invest in education," "cut taxes for working families" and "energy independence."

No doubt those phrases poll well, but nearly all of them could have been in a John Kerry ad - or a John McCain ad, in fact. No mention of health care, no grander theme than putting the "middle class ahead of corporate interests" (surely a good thing), and thus no real chance to define the economic choice in this election.

Move No. 3: Think Bigger.

Obama shouldn't just say that the Republican economic vision is wrong, but that he has an alternative vision that's up to the challenge of the moment - a challenge that voters believe, according to Democratic pollster Stan Greenberg, looks more like the travails of the Great Depression than the economic challenges of the 1970s or 1990s.

In a phrase, he needs a "security and opportunity" agenda - one that tackles the declining economic security of most Americans to ensure that everyone has the ability to reach for and achieve the American Dream.

Republicans have said that American entrepreneurs need protections from risk to ensure they'll fuel our dynamic economy. Obama should insist that American families receive the same sort of guarantees: an affordable health plan that can't be taken away, guaranteed retirement income, a college education within their means, adequate savings and income protections for a rainy day.

Such an agenda, carefully packaged and persistently pitched, would allow Obama to attract middle-class voters who have lost ground. Many of these voters still believe in the American Dream of advancement yet have come to believe that having a reasonable income doesn't deliver the basic security necessary to look toward the future with confidence rather than fear. All Americans need security to achieve opportunity. Obama needs to tell them how he will provide it.