MJ Rosenberg's latest:

…acting alone would undercut him if in the next three years he needed Congressional authority for his next military confrontation in the Middle East, perhaps with Iran.

If he made the decision to strike Syria without Congress now, he said, would he get Congress when he really needed it?

In other words, attacking Syria now makes it possible to attack Iran later.

On the one hand, revealing this motivation will be a political plus with Congress which, following AIPAC (and the donors it directs), repeatedly and loudly declares that if Iran does not capitulate to Netanyahu’s demands, it must be bombed.  Telling AIPAC and Netanyahu that Congressional authorization for bombing Syria  is a prerequisite for bombing Iran is a sure way to get the lobby to get its forces in line for a “yes” vote.

On the other hand, Obama signals to the American public at large that attacking Syria could turn out to be considerably larger than a single surgical strike. It could be the prelude to an infinitely larger war.

It is doubtful that public opinion will accept this rationale. More likely, it will lead to intense pressure from the grassroots to defeat the Syrian authorization. Americans  (in)famously supported a “war to end all wars.” But supporting a war to start more wars seems unlikely.

Stopping a war with Syria is apparently the best way to prevent war with Iran. Congress needs to vote “no.”
http://mjayrosenberg.com/2013/09/01/obama-says-he-needs-congression...