Democrats can’t concern themselves with how opposing strikes against Syria might harm the president. Nothing harms a president more than embroiling this country in a foreign conflict that we cannot resolve satisfactorily. It’s a mistake to think too hard about what a ‘no’ vote will mean for the president or the country or for future presidents. If we don’t intervene in Syria, we will have made an incredibly smart choice and we will reap benefits from that choice every single day. Should we discover that Iran is making a nuclear weapon, it will be easier to deal with it if we don’t have troops dedicated to Syria. If we refrain from taking a unilateral action now that has little international support, we will have more capital to take such an action, if needed, in the future.
If your friend promises to jump off a bridge, no one says that they’re worse off when you talk them out of it because their credibility has been damaged. Everyone knows that they are better off.
The exact same thing is true with this situation.