I believe players declare blockers and blocking order at block step, and then pass priority back to the attacking player, who then passes priority back to the defending player before proceeding to damage.
So then, if the defending player plays a buff on one of (either) of his defending creatures (after blocks/order declared), the attacking player cannot at that point change how they set the blocking order. His creature must deal lethal damage to the first creature he originally chose in blocking order (left to right) before it deals any damage to the second creature in the blocking order.
You have it correct.
Blocking order is set once blockers have been declared. If something changes after this due to a combat trick, then the attacker can't change the blocking order. They still have to deal lethal damage to the first blocker before being able to hit any other blockers.
So then, if the defending player plays a buff on one of (either) of his defending creatures (after blocks/order declared), the attacking player cannot at that point change how they set the blocking order. His creature must deal lethal damage to the first creature he originally chose in blocking order (left to right) before it deals any damage to the second creature in the blocking order.
My question is-- is this a correct analysis?
Blocking order is set once blockers have been declared. If something changes after this due to a combat trick, then the attacker can't change the blocking order. They still have to deal lethal damage to the first blocker before being able to hit any other blockers.
Hope that helps.