If things don't start looking better for Mitt Romney soon, they're going to get a lot worse for him, and very quickly. 

To understand the Romney campaign's nightmare scenario, you need to understand the Romney campaign's much-vaunted finances. It's become conventional wisdom that the Romney campaign has more money than the Obama campaign. But that's not quite right. 

Jim Young/Reuters

If you just compare the Romney and Obama campaigns, Obama's actually got a cash advantage. Up until August, the most recent month for which fundraising numbers are available, Obama raised $337 million to Romney's $194 million. He's also got about $88 million on-hand, as compared to Romney's $50 million. That's in part because Romney wasn't the clear nominee until a few months ago, leaving Republicans who wanted Obama out of office unsure where to put their money. Many of them sent that money to the Republican Party itself.

For that reason, the picture looks better for Romney when you add in the money raised by the Republican National Committee and the Democratic National Committee. The RNC has raised $189 million to the DNC's $111 million, though the joint Obama/DNC "Victory Fund" has raised $291 million to the Romney/RNC's $207 million, and, for technical reasons related to the number of small donors, more of that money is available to the Obama campaign than to the Romney campaign.

Romney's financial advantage only comes clear when you add in the Republican-affiliated super PACs. The major pro-Romney super PACs — American Crossroads and Restore Our Future — have raised more than $150 million, and are able to raise more seemingly at will. The major pro-Obama super PAC — Priorities USA — has only raised $34 million.

But here's the catch: Romney only controls the money raised by his campaign. The money raised by the RNC is controlled by the RNC. The money raised by Karl Rove's American Crossroads super PAC is controlled by Rove and his partners. And while these groups want Romney to be president, they are not solely devoted to the task of electing Romney as president. If they are devoted to anything, it's to blocking Obama.

Which leads to Romney's nightmare scenario: If things don't turn around for Romney soon, those super PACs may give up on the task of electing Romney as president and turn to the task of encircling Obama's second term with a Republican House and a Republican Senate.

Consider the numbers they're looking at. A week ago, Obama was leading by 3.1 percent in RealClearPolitics' average of polls, and he had a 74.8 percent chance of winning the election in Nate Silver's electoral model. But that was supposed to change: Obama's convention bounce was dissipating, and the plan was for Romney, the RNC and the super PACs to flood the airwaves, creating the conditions necessary for Romney to mount a comeback. 

One week later, Obama is up by 3.7 percent in the polls, and up to 77.6 percent in the model.

Instead of narrowing the gap, Romney had a terrible, horrible, no good, very bad week. Will the "47 percent" comments and the almost comical tax returns and the apparent infighting inside the Romney campaign do much to hurt Romney in the polls? I doubt it. But they're not going to help. And they're not going to comfort donors looking for signs that Romney knows how to turn this thing around.

After all, Romney's deficit in the polls is not a momentary blip. He hasn't led in the polls since 2011. And as Robert Erikson and Christopher Wlezien point out in 'The Timeline of Presidential Elections,' in the last 15 elections, which are all the elections we have accurate polling for, every candidate who has led in the polls at this point in the cycle has gone on to win in November. It would be literally unprecedented for Romney to mount a comeback at this stage.

Which isn't to say it can't happen. But time is running short. Romney's probably got at least until the first debate to show he can make up some ground. But if he's not able to make some big gains soon, his last remaining advantage could collapse.

The RNC and the super PACs know that their money is becoming less and less useful in the presidential race. At this point, voters know Obama very well, and they know Romney well enough. Swing state voters have seen enough ads to last them a lifetime. Sinking a few more dollars into the presidential campaign just isn't going to do much. The same can't be said for House and Senate races, where voters have less information about the candidates and are more susceptible to advertising.

At some point, if Romney looks likely to lose, the RNC and the super PACs are going to move to a strategy of damage control, flooding House and Senate races with cash in order to assure that most anything Obama attempts to do in a second term will have to make it through a Republican Congress. Making matters worse, interest groups that were betting on a Romney victory might switch sides in a last-minute attempt to curry some favor with the Obama administration, further starving Romney of the funds necessary to mount a comeback. 

If that happens, then Romney goes from being likely to lose to being almost certain to lose, as his apparent cash advantage is, along with the possibility of a miracle at the debates, pretty much the only thing keeping him in the game. 

Further reading:

- Washington Post: "Romney fundraising hits a snag."

- National Journal: "Romney fundraising comes down to earth."

- Politico: "Republican superPACs hit a crossroads."

- NYT Magazine: "How much has Citizens United changed the political game?"