Is the Secret Service plotting to help assasinate Obama?

Security around Obama events has raised blogosphere concerns. Is the Secret Service under orders to give Obama lax security? Are they incompetent? Or is there another explanation?

The observed facts are that the Secret Service only checked the first people to arrive at a number of Obama events. With long lines at the screening points shortly before the event the Secret Service suddenly let the rest of the audience in unchecked.

Before we cry conspiracy its worth remembering a couple of issues. First the likelihood that the Secret Service would allow itself to be complicit in an assassination plot. That would be entirely counter to the whole service ethos. Guarding the President is the task the Secret Service takes most seriously. These are people with unique access to high ranking politicians. It would only take one member of the Secret Service to voice concerns to Pelosi, or Reid, or Carter or Clinton or any of the other senior politicians that receive regular secret service protection for a plot to be utterly blown.

The other factor that counts against it being a plot is that no assassination attempt was made. An attempt to deprive Obama of adequate security makes no sense at all unless there was a plot to make use of that weakness.

More likely by far is that this is exactly what the Secret Service claims, an intentional part of the security plan. The principal security concern at a large event like these would be a short range attack by a suicide bomber or someone with a pistol. A person standing at the back of the crowd is going to find it rather difficult to assemble a sniper rifle and take aim. Any areas where a sniper could work undisturbed should be guarded.

The history of political assassinations since the murder of JFK has been the close range attack - the assassinations of JFK and Bhutto being typical examples. An assassin wanting to attack Obama would be looking to get in close. That would almost certainly require them to arrive early.

The question then is how the Secret Service was managing the audience. Was it possible for someone who arrived late to reach the areas closest to the candidate? Was there an explicit separation?