What particularly worries me about Hillary Clinton's continued hawkishness on Iran is its basic coherence. Clinton, more so than any of the other candidates, really is speaking, legislating, and voting with her eventual presidency in mind. She's been making a real effort not to offer critiques, or support popular legislation, that will harm her capacity to pursue her eventual agenda. That's fine and well and good. But on Iran, the whole picture is a little worrying.
So we know Clinton is an "all options on the table" type who's repeatedly said that Iran cannot be allowed to achieve nuclear weapons. We know she voted for the Lieberman-Kyl amendment which, in point of fact, was a way of creating an underlying case for attack. I used to be worried that these moves would help give Bush credibility for attacking Iran. Lately, I'm more worried that they help give Clinton an eventual argument for bombing.
To be sure, there's some contradictory evidence here, most notably, the resolution she co-sponsored with Webb to force Congressional authorization of any attack against Iran. It's a good bill, and would, if passed, effectively hamstring Bush. But it probably wouldn't hamstring Clinton, who could almost certainly pull together a coalition of hawkish Republicans and centrist-to-liberal Democrats to authorize an attack on nuclear facilities, and could use such already-passed resolutions as Lieberman-Kyl to make the argument.