Nobody understands the divide-and-conquer strategy better than the children in your home. They have an instinct for it. When one parent stands in opposition to a desired outcome, a child will attempt an alliance with the other. If successful, the strategy is reinforced and is likely to become a repeated pattern of family interaction, often leading parents into states of confusion or even conflict between themselves.
Your child needs parents who know how to stand firm together. A healthy alliance between father and mother creates a secure environment in which children are more likely to attain appropriate emotional and behavioral balances as they grow. So, how strong is your parental alliance? Do the two of you cooperate well, or do you often work against each other?