Willingness to take "yes" for an answer.
Almost the entire world, and most of Congress, believes this:
1) Syrian regime forces launched a prolonged, widespread, massive artillery attack including a lot of artillery rockets full of Sarin gas that killed a large but unknowable number of people (probably somewhere in the 400-1400 range), including many civilians.
2) The USA responding to this attack with cruise missile strikes within Syria is not a good idea and should not be done.
That is a huge win, if one is able to take "yes" for an answer.
Or, one can cling to gainsaying #1 and maintain a theory that all these American allies and mainstream politicians that oppose the war don't have a clue about what happened.
If the UK and Germany are so stupid as to believe a "lie" (that regime forces launched a really serious attack) then there is little meaning in them opposing the war, since they don't have a clue about the situation.
Really, there is a global peace consensus out there that is winning the day while not being the least bit challenged or troubled by #1.