A few months ago, Nate Silver asserted that jobs reports "that come in at under 150,000 jobs could put [Obama] on a trajectory toward defeat." Nate has now lowered the bar to 125,000 jobs a month. He warns that the relationship isn't precise:
Certainly, if the economy creates 200,000 or more jobs per month throughout the rest of the year, as it did in January and February, then Mr. Obama is likely to be in pretty good shape. And if it averages 75,000 or fewer jobs per month — that’s about the point at which the rate of job growth will lag that of population growth — he is likely to be in some trouble. Anything between about 100,000 and 175,000 jobs per month, however, should leave both Mr. Obama and Mitt Romney with ample room to debate the nuances of job creation and the rest of the economy.
The Dish 