That's not a safe strategy with less than perfect information. If as few as 5 of those gray-supporters vote black secondary when you thought they'd vote white, you've just handed the election to your worst enemy, when by voting honestly you could have had the moderate, agreeable-to-all candidate.

As a wider assortment of fringe parties become involved, perhaps emboldened by their nonnegligible first-round numbers, that sort of strategy becomes more sensitive to secondary (and tertiary, etc.) preferences. As part of that same increasing complexity, secondary preferences become more difficult to meaningfully survey in advance.