Quote Originally Posted by PokerPatNEU
If you check and:
he has the Ace, he'll bet the river and then call your push.
he has Kx (KQ most likely), he might try a value bet or a semi bluff hoping the four flush missed you.
he has a slow played set, he might try a value bet or a semi bluff hoping the four flush missed you, especially if he has the 4s.
Why would any non-flush hand (2 pair, any set, etc) ever do anything but check behind on a 4-flushed board when last to act? No worse hand is calling. If he has KQ and you check to him, he is going to check behind.
So what you're saying is they're much more likely to call an overbet than try to make one themselves? (We agree you're taking the ace of spades's stack regardless if you check or bet?)