The announcement a week ago of 10.2% unemployment is a significant political event for President Barack Obama. It could well usher in a particularly serious crisis for his political standing, influence and ability to advance his agenda.

Double-digit unemployment drove Ronald Reagan's disapproval ratings in October 1982 up to a record high 54%. It was only when unemployment dropped to 7.3%, roughly two years later, that he was able to win a landslide victory over Democratic challenger Walter Mondale in the 1984 presidential election.

Similarly, Franklin Roosevelt's success in the 1930s in reducing the 25% unemployment rate he inherited down to the mid-teens was almost certainly responsible for his success in the 1934 midterm elections and in the 1936 presidential elections.

Mr. Obama faces a similar challenge. A detailed look at the available survey data suggests that the difficulties may be more substantial than those suggested by the recent off-year elections.

Mr. Obama's approval among likely voters has dropped to the low-50s in most polls, and the most recent Rasmussen Reports poll of likely voters shows him slightly below the 50% mark. This is a relatively low rating for new presidents. Mr. Obama's approval rating began to slide in a serious way in early July, triggered by a bad unemployment report.