That is pretty much it. Although some brokers will liquidate you if you fail to meet the margin call in a timely enough manner, especially if you suddenly go under water. That is a gamble though, a really really huge one, if you are relying on that.

If the trader is stuck in that position, possibly a hedge by buying one of the back months might save him. I got caught in a limit move against my position in corn once, and saved my account by entering a less active month. Well, I should say my guy at Alaron did, as I had no idea what I was doing back then.