The greatest cause for Rome's downfall was their weak political power. The reason I choose political was because when a government is strong they are usually able to keep control of the nation and keep the citizens happy. In Rome's case their government failed to discipline, train and supply the Roman army.
Without discipline their was no leadership among the Roman ranks. It was the government's fault that Rome declined because the citizens lost faith in the emperor which caused the emperor to loss power. Also due to the weak government roman citizens stopped participating in public works. After the Pax Romana most of Rome's emperors were not qualified for their power status and used it to help themselves and not the empire.
Many Roman Emperors were self centered and didn't care about their citizens. Also The government failed to stop the people who often revolted against the empire, which set a example that Roman power was weak and encourage more revolts and eventually invasions by foreign forces. The government also was very vulnerable to corruption because of it's small amount of people who had and input in politics.
Lastly Rome's government spent most of it's time and money on projects that didn't make Rome stronger and more united, the people became angry and refused to participate in public works. That is why political power was the ultimate cause of the downfall of Rome.
