Final answer:
The Tonkin Gulf resolution allowed Johnson to escalate military operations in Vietnam without needing specific congressional approval for each decision, greatly increasing the power of the president.
Step-by-step explanation:
The effect of the Tonkin Gulf resolution was that Johnson took the nearly unanimous approval as reason to use the resolution as a substitute for a declaration of war. This allowed him to escalate military operations in Vietnam without needing specific congressional approval for each decision. The resolution dramatically increased the power of the president and transformed the American role in Vietnam from advisor to combatant.