Calling a Possible Bet On the Come

Secondly, in stud and hold 'em games, it is usually a mistake to raise with a good but not a great hand when you think your opponent - particularly a very tough opponent - has bet or raised on the come for a flush or a straight. If his bet was legitimate, he probably has you beat, so you're simply donating money to the pot. If he was on the come, he has an easy call of your raise, which eliminates most of the reasons for you to make it. Thus, even if you were quite sure that the Q♠J♠9♠ earlier in this chapter had only a four-flush, you would not be correct in raising. You would only call.
However, when you call an opponent who you think is on the come, you usually do so with the intention of betting right out on the next round any time that opponent draws a blank card that would not make his hand if he was in fact on the come. You now become the favorite if your opponent was on the come, and you don't want to give him a free card.
There is a mathematical reason for you to play your hand this way. Let's say you bet with two cards to come, and someone raises you. You estimate that there is a one-third chance that player has you beat and a two-thirds chance he is on a draw. Nevertheless in most cases he is still a mathematical favorite. So you can only call the raise since you're the underdog. However, when the next card cannot have made his flush or straight if he was drawing to it, now, with only one card to come, you have reverted to being the favorite. So you should usually bet. On the other hand, if that card makes the possible flush or straight, you should usually check and fold if your opponent bets, unless you are getting good enough pot odds to chase. Your opponent almost certainly has you beat, whether he was originally betting a legitimate hand or betting on the come.
Here is an example of this calling defense against a possible semi-bluff that came up when I was playing recently in a seven-stud game. I started with a three-flush and a 10 showing and was lucky enough to make three 8s on fifth street. I bet, and a good player who caught a K♥ with the J♥ as his door card raised. I reasoned the raise meant one of three things. Either my opponent had started with kings in the hole, in which case he was raising with the best hand; or he had started with two jacks, made kings up, and raised, figuring I was betting 10s and 8s; or he had a flush or a straight draw. I called the raise. When no heart, ace, or 9 fell on sixth street, which might make a straight or flush, I bet right out, much to my opponent's surprise, for my opponent had been expecting to get a free card. It turned out the opponent was in fact on a flush draw with a small pair, and the three 8s held up. (Of course, if a heart, ace, or 9 had fallen, the play in this instance would have been to check and call since there was a reasonable chance for me to make a full house on the last card.)