iI also suspect that Kerry's "accidental" solution was no accident. Not that he can't misspeak, but because Russia replied with a relatively developed plan within 3 hours and Syria joined in within a half hour of Russia. 
Now I know that both countries can move faster than democracies, but this is really not that believable.  I suspect that Kerry had socialized the idea with Lavrov - and likely with Ban Ki Moon.  Therefore they would have thought out the possibility. 
I don't think he would do this without Obama's approval as he is very loyal and respectful -- but if he saw this as a possibility to avoid war, stating it as an almost throw away solution is a way to do it. Obama still has the prerogative of accepting or rejecting it.  
Incidentally The US media did not report - as the BBC did - that Kerry would not rule out that Obama would decide to wait for the UN report as "our friends" suggested and he held open the possibility of another try for a UN resolution.  
I would assume that if this is rejected,  then support for an attack will be even less than it is - it will reduce to just those who wanted a war before the attack - losing people who thought that  chemical weapons were something that needed to be responded to.  I know I would move from conflicted to absolutely not. 
I was surprised at Hillary Clinton's comment that this would be a "first step" to avoiding an attack. I know it is consistent with her having been an advocate as SOS for doing more, but I always thought of her as more political.  There is NO way that being to the right of Kerry on this (and likely Obama but we don't know yet) - could be the way to the nomination.  I know DU is not representative, but I really do not think there is any desire to go to war.