If Trump pushes us into a war, we will HAVE to be antiwar.
Any conflict he throws us into going to be senseless, immoral, protracted and unwinnable. Trump will force his generals to use both brutal and ineffective tactics, tactics that will not only prolong the fighting but cause heavy losses among the forces of this country and any other country foolish enough to ally itself with Trump(not this country, just Trump) and what he will inevitably see as his personal army. Any short-term support for such a conflict in the polls will evaporate in months, as support for the Iraq War did, when reality seeps through whatever truth-filters Trump installs. Any long-term popular backing for a Trump-initiated conflict will be concentrated almost exclusively among people who would never, under any circumstance, even consider voting for this party.
The only chance we will have to keep this party going, let alone move it into a position to actually win any elections held during that war, will be to find courage, stand up, and loudly proclaim "This is WRONG. It must stop. We will end it as soon as possible".
No halfway position, no "we can do it BETTER" stance, can possibly be a responsible position, or have any chance of carrying the day in such a situation. Life and death cannot be triangulated.
If he says "War", we MUST say "Hell NO!".
That is the lesson of recent history.