What a difference a month makes.

Four short weeks ago, McCain and Obama were running neck and neck, and concerned outsiders (like me and Bill Galston of the Brookings Institution) were calling on Obama to sharpen his message, especially on the economy. (Galston began his open letter to Obama: "You are in danger of squandering an election most of us thought was unlosable.") The cover of the last issue of TNR had a picture of Obama next to a single word: "WORRY."

It all seems so long ago. The election really does look "unlosable" now. The economy is far and away the biggest issue for voters, and Obama is creaming McCain on it. If things stay as they are, we're looking at a blowout of historic proportions--and the first clear mandate for economic reform since Reagan's win in 1980.

So what happened? The obvious (and correct) answer is the meltdown of our financial system. But why did it help Obama so immensely and destroy McCain so completely?

The standard models of presidential elections can help a little here, but only a little. Most of them showed a strong Democratic year--more or less a two-thirds chance of a Democratic victory and a probable three- to four-point vote spread. But these models focus on overall economic growth or the job market, and Obama's rise been much sharper, and his margin may well be much larger, than standard indicators would predict.

To my mind, the financial crisis had two massive salutary effects for Obama. First, it has laid waste to two core tenets of conservative economic philosophy: the "ownership society" and trickle-down economics. As the housing and stock markets have plummeted while the job market falters and health security erodes, Americans are facing up to much graver economic risks than they have for more than a generation. The crisis has also put a vivid face on America's winner-take-all inequality: the Wall Street fat cats who made out like bandits when the housing bubble was expanding by shifting risks (and now costs) onto the rest of us.

There's also a more specific reason for the turnaround: Obama stepped up to the challenge. On the economy, Obama has shown brilliance in the past (such as his remarkable speech on financial market regulation made earlier this year), and his policy proposals have been sensible. But there has been a lack of punch and vision to his critique of the economy's direction. Indeed, it was McCain who was using concern about gas prices to keep the race surprisingly close.

But Obama's bland commitments on the economy now seem a distant memory. With focus and eloquence, he has been saying over the past few weeks that this election is about restoring economic security and opportunity to the heart of the American Dream-for the middle class and for those who aspire to be middle class.

"Together, we cannot fail. Not now. Not when we have a crisis to solve and an economy to save. Not when there are so many Americans without jobs and without homes. Not when there are families who can't afford to see a doctor, or send their child to college, or pay their bills at the end of the month. Not when there is a generation that is counting on us to give them the same opportunities and the same chances that we had for ourselves."

"There is a crisis to solve and an economy to save." That is exactly what he needs to emphasize. People know there is more to this thing that some fat cats who screwed up their accounting and lost a bunch of money. This crisis has allowed them to admit that there is something fundamentally wrong with our economy that needs attention.

Obama is now taking exactly the right rhetorical approach to get the mandate he needs to end the thirty year experiment in marketing aristocratic snake oil to the middle class by presecribing tax cuts for everything that ails them. If he wins with the kind of mandate it looks like he's going to get, he'll have the political capital to truly put the trickle-down, ownership society nonsense in the past where it belongs. Where it always belonged.