There are two developments today in the presidential race that combined create real problems for President Obama’s reelection. The first is the Romney campaign’s decision to go after the president’s stimulus package, labeling it a failure and the “ultimate earmark” program. The second is that a group of super PAC warlords, led by the Koch brothers, will spearhead a billion-dollar independent expenditure to defeat Obama.

First, the stimulus attack. While the initial foray was a little ham-handed (Karl Rove’s Crossroads video called Obama’s spending “public equity,” to counter attacks on Romney’s private equity), there is a potent idea here. The charge should go like this: The president spent billions of your tax dollars on pet projects that have either failed outright or failed to create jobs anywhere near the promised number. This attack could combine the president’s two biggest vulnerabilities: government spending and the continuing, historic weakness in the economy. And there are many examples of “failure” in the stimulus bill, some of them in target states where Romney’s forces can introduce them in serial fashion.

Of course, Obama has a strong comeback: The stimulus did work in a crucial way; it saved the country from a depression and laid the basis for the slow recovery we witness today. And there are many more success stories than failures: jobs saved and created, roads built, schools renovated and so on. But will Obama have the resources to make this counterargument effectively in the face of a Koch brothers onslaught? What I feared many months ago seems to becoming true: Obama may be the first president in modern history to be dramatically outspent by his opponent, and that creates a fundamental challenge for his reelection. More on that this afternoon.