John McCain offers up a perfect example of a false choice on Syria:

Would you rather have these weapons – perhaps some of them – in the hands of the wrong people, or would you rather have [Syrian President] Bashar Assad prevail and then encourage Iran to further their ambitions on nuclear weapons?

Republican Syria hawks have been eager to link the conflict in Syria with Iran’s nuclear program in part because even they know that their demand for arming the Syrian opposition is extremely unpopular, but that is no reason for anyone else to take this link seriously. The truth is that the U.S. could arm the Syrian opposition and Assad might still hold on to power anyway. Indeed, McCain wants U.S. military action in Syria because he assumes that to be true. If Assad holds on to power, it doesn’t follow that this would affect the nuclear issue at all. If it did affect the nuclear issue, it would more likely produce the opposite result of the one McCain imagines.

It’s quite possible that the overthrow of Assad could make Iran’s leaders more paranoid about Western efforts to depose them and therefore make them more likely to want a nuclear deterrent against attack than they would otherwise. The choice that McCain offers here depends entirely on the assumption that Iran will be made more accommodating on the nuclear issue by inflicting defeat on an Iranian ally. To date, no other coercive U.S. policy aimed at undermining Iran’s nuclear program has caused the Iranian government to become more accommodating on this issue, and there is no reason to think that a more aggressive anti-Assad policy would have any more success in doing so.