Democracy is fragile. The Roman Republic became an autocratic empire when loyalty to individuals became more important than the rule of law. (see the related Note: Governments of Men and Laws). The events at the end of the Roman Republic and during the Roman Empire remind us that most people, over time, have not lived with anything resembling the freedom and prosperity that we have today in western democracies. The founding fathers of the United States took inspiration and lessons from Greek and Roman experiments in democracy.
The Example of Rome
The dictators at the end of the Roman Republic slaughtered their enemies and appropriated assets to secure their power and fund their ambitions. The only law was what the leader and his loyalists wanted. The only truth or justice was what the dictators claimed.
John Adams, the second president of the US wrote a defense of the US Constitution, that concluded in volume 1:
"All nations, under all governments, must have parties ; the great secret is to control them : there are but two ways, either by a monarchy and standing army, or by a balance in the constitution. Where the people have a voice, and there is no balance, there will be everlasting fluctuations, revolutions, and horrors, until a standing army, with a general at its head, commands the peace, or the necessity of an equilibrium is made appear to all, and is adopted by all."
-John Adams, 1799, A Defence vol ILetter LII by John Adams looks to Rome as an example:
"We have before seen, in the history of Rome, with what eagerness the aristocracy pursued and demolished the monarchy : the kings are commonly reproached with tyranny, and the nobles are applauded for resistance to it; but it is clear that the nobles were as tyrannical, and that their eternal plots and conspiracies against the kings, their power, their crowns, and their lives, were the cause and the provocation to that tyranny. It is impossible to say which were worst, the nobles or kings; both certainly were bad enough in general, and both frequently violated the laws, as it will ever happen when there are but two branches. The people as yet had no adequate power to aid or controul either."
-John Adams, A Defence, 1794, Letter LII and concludes
"This commonwealth, by the splendour of its actions, the extent of its empire, the wisdom of its councils, the talents, integrity, and courage of a multitude of characters, exhibits the fairest prospect of our species, and is the most signal example, excepting England, of the wisdom and utility of a mixture of the three powers in a commonwealth : on the other hand, the various vicissitudes of its fortune, its perpetual domestic contests, and internal revolutions, are the clearest proofs of the evils arising from the want of complete independence in each branch, and from an ineffectual balance."Partisan Politics
John Adams was embroiled in deeply partisan election battles - first in 1796 when he won and then again in 1800 when he was up for re-election and lost to Thomas Jefferson. Jefferson became our third president. In case we think politicians were more honorable and dignified in 1800:
Jefferson paid for James Calendar's attacks on Adams. Callendar published this book "The Prospect Before Us" that opens with: "The design of this book is to exhibit the multiplied corruptions of the Federal Government, and more especially the misconduct of the President, Mr. Adams."
Callender was sentenced to jail under the sedition Act, but pardoned by Jefferson.
Although Adams was certainly not happy about losing he peacefully transitioned power to Jefferson. The depth of his thought on the structure of government and the constitution is even more impressive 225 years later as we can see how the constitution has stood up over time with many societal and technological changes.
Transitions between dictators and later emperors were defined by the dictators and emperors unless a more powerful warlord came along and took over by force. There was no "voice of the people" only voice of the most powerful. In AD 69, 4 emperors competed for the throne, Galba, Otho, Vitellius, and Vespasian. In the end, Vespasian won and he and his sons ruled until Domitian was killed and Nerva became emperor and so began another dynasty, the Nerva-Antonine dynasty. With each transition was an opportunity for civil war.
The Death of Trajan
Turning to the topic of ancient coins: Trajan had not clearly defined his successor. Trajan died August 8 or 9 in AD 117. On his death bed, he named Hadrian as his successor - at least that is what the letter signed by Plotina said. Hadrian was 41-years-old and decisively took control, and had he not, there might have been another period of civil war.
This coin is a very early issue of Hadrian securing his transition as successor to Trajan. This coin lacks the word added later, "ADOPTIO", in exergue. However, on this coin the words "DIVI TRAIAN AVG F" declares Hadrian as "son of deified Trajan". Also worth noting that this coin inappropriately carries over the titles of Trajan for Hadrian (e.g. OPT GER DAC PARTH) - titles that were later not included on coins of Hadrian.
Hadrian, AD 117-138, AR denarius (18.9mm, 3.32g, 7h), Rome mint, struck AD 117
Obv: IMP CAES TRAIAN HADRIAN OPT AVG GER DAC, laureate, draped, and cuirassed bust right
Rev: PARTHIC DIVI TRAIAN AVG F P M TR P COS P P Trajan presenting globe to Hadrian, each holding scroll
Ref:RIC II 2c p.338
If Hadrian had not succeeded in managing the transition, the empire could have turned back to civil war to determine the next emperor. You can find a nice write-up of this transition here on the excellent site "Following Hadrian". There is also a useful article about the aureus which might provide additional evidence that Trajan intended Hadrian as his successor.