[memphis57]

IMO, check-call is the only way to go in the absence of a read that strongly suggests a flush. Checking rather than betting saves a BB if there is a flush, but also encourages him to bet with nothing since you led up now, hence the call.

In the absence of indicators to the contrary, the odds of two random cards that you haven't seen both being spades is only 4% (10/45 * 9/44). Now the fact that MP1 has been calling with something raises those odds somewhat, but think of alol the other cards he could be calling with. I'd put the odds of a flush under 50%, far below the 90%+ you would need to justify not calling one more bet.