It’s conventional wisdom that Barack Obama and the Democrats have to use their convention to persuade swing voters. OK, but how? That’s the big question. It doesn’t seem at first blush that the famous Reagan question that’s resurfaced—“Are you better off than you were four years ago?”—will work to Obama’s benefit. But it’s possible that it can, as long as Obama and the other speakers weld it tightly to another question that needs to go something like, “And how well off do you think you’ll be four years from now?”

But first, let’s review last week quickly. It was not history’s most successful convention. The bounce appears to be minimal, and it seems unlikely that many swing voters were highly impressed with the case the Republicans made. They showcased some Latino talent, and Mitt Romney talked about women for six minutes. But the real centerpiece of the convention, chairs aside, was Paul Ryan, and while he tried to come off as reassuring to moderates, his speech was such a mansion of mistruths—a fact, I think, that the Democrats communicated pretty effectively over the course of the week—that most swing voters didn’t come away with Ryanmania, according to the numbers.

So the Democrats have a big opening. How to take advantage of it?

To begin with, Obama can certainly make the case that the country overall is better off than it was four years ago. The month he took office, the country lost 818,000 jobs. The next few months were similar. On the day he took office, the Dow Jones average stood at 7,950. It’s now above 13,000. That means a lot of retirement plans have come back to where they once were and then some. Of course there’s the auto bailout, which is relevant to all of us, but especially relevant in key states. And there are the positive effects of the stimulus, which as I noted over the weekend, he should not be afraid to tout.

Obviously he’s got to be careful about how he talks all this up. We still have 12.8 million people unemployed and looking for work. If Obama presses on this good-news accelerator with too heavy a foot, the engine will backfire in a big way. He has to throw in the expected caveats, of course, but he also has to regulate the rhetoric with great care. Remember: The day after the convention ends, we’re getting the August jobs numbers. The early indicators are decent, pointing toward 140,000 or so, which is a pretty encouraging number for him politically, but if he gets smacked with a five-digit number the day after a speech when he tries to talk up the economy, there goes his bounce.

I like that there’s something Rovian about this, or reverse-Rovian: turn weakness into strength. With the right set of facts, he can do it. But the real sale to swing voters will come with the second half of the equation.

This convention must be merciless on what the Republicans are going to do to this country economically. Attacks on Romney should have nothing to do with his personality or his hair or his preference for “quiet rooms” (well, a little of that) or his friends’ and supporters’ empty chairs. It should be almost all policy. That, to invert the famous line from Captain Renault in Casablanca about his heart, is Romney’s most vulnerable spot.

I hope and expect that this convention will pound away on tax cuts for the wealthy and cuts to Medicare, yes. But there’s more. There is Romney-Ryan’s stated plans to repeal Dodd-Frank and let the banks go wild again. The banks caused the problem in the first place, and the idea that they want to repeal Dodd-Frank should be enough to signal to swing voters that a Republican administration is blithely delighted to risk the same kind of crisis happening again. Something tells me that Bill Clinton (um, never mind that Glass-Steagall repeal) can really drive that point home.

The Democrats—Joe Biden, Clinton, Obama himself—have to talk some serious smack on GOP economic plans and fantasies and paint a lucid, stark, but completely fair and accurate picture of an opposing campaign that wants to be George W. Bush on steroids. I hope they’re not afraid to dig into some detail and explain how Romney’s plans to cap domestic spending, raise defense spending, slash taxes, and balance the budget all at same time just doesn’t come close to adding up, and will, as I’ve explained previously, lead to both massive domestic cuts and huge deficits.

When Democrats talk details, they win. Because the facts are on their side. When the conversation takes place at the level of banal generalities—Big government! Low taxes!—that’s when Republicans win. People—moderate people—agree with Republican slogans, but once you explain to them what those slogans are going to mean in practice, you peel a sizeable number of them away.

That’s the job this week. It is true that the undecided vote is small to start with, and there isn’t much room for a bounce. But the Democrats can get two or three points out of this week, which may be all they need, and, unlike the Republicans, all they have to do is tell the truth.