Dismal. Disappointing. Grim. Gruesome. Pathetic. A punch to the gut. Needless to say, the Labor Department’s May jobs report is not inspiring optimism among most commentators. After months of relatively promising jobs data, the U.S. added just 54,000 non-farm payroll jobs in May (compared to 232,000 in April and well below the 150,000 net jobs economists had projected). The May figure represents the weakest gains since September 2010. Meanwhile, the unemployment rate ticked up to 9.1 percent, from 9.0 percent. Who’s to blame? Here, four possible culprits:

1. President Obama
Success has many fathers, but failure has only one — and his name is Barack Obama, says Don Surber at the Charleston Daily Mail. The president’s $787 billion stimulus package failed to lower unemployment, as did the Fed’s $600 billion quantitative easing measures. Put simply, Obama "has not been a jobs president," says Taylor Marsh at her blog. "He hasn't spoken to the issue in any way that resonates. It's like he doesn’t understand how people are feeling." That might spell big trouble for the incumbent president, says Binyamin Appelbaum in The New York Times. "No American president since Franklin Delano Roosevelt has won a second term in office when the unemployment rate on Election Day topped 7.2 percent."

2. Congress
"Any sane person should look at these numbers and conclude that the economy desperately needs a boost," says Steve Benen at Washington Monthly. Instead, Congress is hyper-focused on debt reduction, "which takes money out of the economy and makes unemployment worse." Here's a wild idea, says Felix Salmon at Reuters. Perhaps Capital Hill's "bickering politicians [should] stop playing stupid games with the debt ceiling and start concentrating on important matters." Oh, who am I kidding? The GOP won't do anything helpful "until 2013, for risk that Obama might be able to take credit for it."

3. Mother Nature
Lousy weather was a factor, says Chris Rovzar at New York. "The interruption in Japanese trade and manufacturing from the tsunami affected hiring — as did the devastating tornadoes in the Midwest." Since those are temporary setbacks, job numbers will likely improve soon. Still, the fact that weather was "able to make such a dent in hiring shows how frail the economic recovery actually is."

4. Job-hunting Americans
"There’s a silver lining here," says Daniel Indiviglio at The Atlantic. The uptick in the unemployment rate doesn't reflect mass firings. "Instead, more Americans who had given up on finding a job entered the labor market." In May, more than 100,000 such people started hunting for jobs again. Of course, not all found them. But it's a good sign that so many once-dejected Americans think it's worth looking for work again.