The dealer’s behavior in Blackjack primarily affects your strategy through their upcard and the predictable rules they follow for completing their hand. A weak dealer upcard (like a 4, 5, or 6) suggests they might bust, so you might play more conservatively. Conversely, a strong upcard (like a 10 or Ace) may lead you to play more aggressively. The dealer's pace could also influence how much time you have to think, potentially affecting your decision-making. However, their actions are largely predictable, so your strategy is mainly based on their upcard and the rules they must follow, rather than their individual behavior.