Asking for help in combat

[uttwich]

Quick question that I think I already know the answer to:

If a player is in combat where they are currently winning, can they ask for (and accept) help to prevent someone from playing one-shot cards? Or can they only ask for help if they are currently losing? (I think it's the latter, but wanted to make sure.)

If it is the latter, it looks like the only exception that I am aware of in the original Munchkin series is the Perfectly Ordinary Bunny Rabbit which allows you to ask for help before figuring out what you're really up against.