I'm wondering this too. Additionally, can you reveal your poker card to win a duel as you can in multi player?
I have been playing it that I can reveal my card. Without this it seems like it would be unfairly difficult to win a duel.
Though, there was that one time I spent influence to make the AI re-roll 4 times...and he kept rolling 5/6s, the cheater! (It was still worth it, I effectively traded resources I didn't need to get what I wanted, plus the additional resource for the Wanted card)
I had multiple duels in a single game where the lucky AI rolled 5/6's until I was forced to accept defeat... Funny how I can be so lucky when I am rolling for the AI! Needless to say, I lost that game pretty decidedly.