What the dems are truly scared of is another galvanizing military effort that pulls more voters over to the republican party in the lead up to the next presidential election.
They are not stupid. They realize that Iran is quite different from Iraq in that people are concerned already about Iran and since Iran is not even really pretending anymore that they are seeking nuclear weapons it is a whole different ballgame.
Democrats are stuck with trying to convince people that Iran having nuclear weapons is "ok" or to try and quagmire it away and delay by constant referrals to the UN in the hopes that they can belay any military effort that would bring more people to the presidents side.
Right after we went into Iraq the dems went crazy about protecting Iran and Syria. Note that Byrd included Syria even though no on eis mentioning Syria right now.
These are two of the worst regimes on Earth, and the dems are hell bent on protecting them. That is why the dems are so vulnerable IF the republicans had the willingness to expose them.