President George H.W. Bush's popularity declined after the Persian Gulf war because Americans thought that bush should focus on domestic policy rather than foreign policy.
Gulf war was a campaign waged by the United States against Iraq in response to the Iraqi invasion
The major thing that declined his popularity was that Americans believe that Bush did not have a clear plan for handling the domestic problems and hired illegal immigrants.
So the Americans believed that bush should focus on domestic policy rather than a foreign policy which led to the decline in popularity after it reached an all-time high after the Persian Gulf war.
Therefore, D is the correct option.
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