But when a president makes such a rare request, he’s sending a clear message that there is an emergency, or at least an urgent issue, that must be addressed in the most solemn national forum. Both Bushes spoke in a time of war, as did Richard Nixon during Vietnam. Lyndon Johnson addressed a joint session after the assassination of John F. Kennedy.

Is Obamacare such an issue? Hardly. So it will be the president’s job to convince the public that the need to pass a national health care bill is so urgent that it ranks alongside war and other national emergencies.

It can’t be done. No matter what Obama says on Wednesday, the audience will see the speech for what it is: A president speaking not as the nation’s leader in time of crisis but rather as a salesman pushing a troubled product.

Sales jobs are the least successful joint addresses.