<<RG>>who cares what their side issues are if they will agreee [sic] to focus on getting the USA out of Iraq.<<
There's the rub. In my experience with leftest groups (esp.), it is very difficult to keep them on the one issue that the alliance was formed for. Next thing, you find that you are in a group that supports nationalized health care, or etc. If the alliance has more than one leftest group... the tendency for them to stray off topic is even greater.
Feel free to give it a try, just don't be too surprised if it doesn't work out.