|Main leaders||Scipio Nasica Serapio|
Cato the Younger
Titus Annius Milo
Marcus Junius Brutus
They formed in reaction against the reforms of the Gracchi brothers—two tribunes of the plebs between 133 and 121 BC who tried to pass an agrarian law to help the urban poor, and a political reform that would have diminished the influence of the senatorial class. As the Optimates were senators and large landowners, they violently opposed the Gracchi, and finally murdered them, but their program was upheld by several politicians, called the Populares ("favouring the people"). For about 80 years, Roman politics was marked by the confrontation of these two factions. The Optimates favoured the ancestral Roman laws and customs, as well as the supremacy of the Senate over the popular assemblies and the tribunes of the plebs. They also rejected the massive extension of Roman citizenship to Rome's Italian allies advocated by the Populares. Although suspicious of powerful generals, they sided with Pompey when they came to believe that Julius Caesar—himself a Popularis—planned a coup against the Republic. They disappeared with their defeat in the subsequent Civil War.
While several leaders of the Optimates were patricians—belonging to the oldest noble families—such as Sulla or Scipio Nasica Serapio, many were plebeians: the Caecilii Metelli, Pompey, Cato the Younger, Titus Annius Milo, etc. Cicero—the most famous Optimas—was even a novus homo (the first of his gens to be senator).
In general, the Optimates favored the nobiles and opposed the ascension of novi homines into Roman politics, though exceptions exist. For instance, Cicero (a strong supporter of the Optimates' cause) was himself a novus homo, being the first in his family to enter the Senate—he was thus never fully accepted by the Optimates. On the other hand, during the civil war of 49 BC Julius Caesar of a respectable old family contended against a Senate championed by Pompey, who was from a wealthy yet recently ennobled family. In addition to their political aims, the Optimates opposed the extension of Roman citizenship and sought the preservation of the mos maiorum, the ways of their forefathers. They sought to prevent successful generals such as Gaius Marius, Pompey and Julius Caesar from using their armies to accrue such power that they might be in a position to challenge the Senate. They opposed Marius' plan to enlist impoverished Romans who were too poor to provide their own arms and supplies in the legions and the generals' attempts to settle these veterans on state-owned land.
John Edwin Sandys detects an Optimates grouping at time of the death of Tiberius Gracchus in 133 BC. The Optimates' cause reached its peak under the dictatorship (81 BC) of Lucius Cornelius Sulla. Sulla's administration stripped the assemblies of nearly all power, raised the number of members of the Senate from 300 to 600, executed an equally large number of Populares via proscription lists and settled thousands of soldiers in northern Italy. However, after Sulla's withdrawal from public life (80 BC) and subsequent death (78 BC) many of their policies were gradually reversed. Besides Sulla, notable Optimates included Lucullus, Cato the Younger, Titus Annius Milo, Marcus Calpurnius Bibulus and Marcus Junius Brutus the Younger. Though the Optimates had opposed him for the entirety of his political career, Pompey also found himself as the leader of the Optimates' faction once their civil war with Julius Caesar began in 49 BC. Optimates who (along with disillusioned Populares) had carried out Julius Caesar's assassination in 44 BC called themselves Liberatores (liberatores meaning "liberators").
Robert Morstein-Max, a historian of the Late Republic, cautions against understanding the terms populares and optimates as solid factions or as ideological groupings:
Our chief contemporary witnesses to the political life of the late Republic, Cicero and Sallust, are fond of analyzing the political struggles of the period in terms of a distinction between optimates and populares, often appearing with slight variations in terminology, such as Senate, nobility, or boni versus People or plebs. [...] The polarity obviously corresponds with the dual sources of institutional power in the Republic – Senate and People [...]. It is important to realize that references to populares in the plural do not imply a co-ordinated 'party' with a distinctive ideological character, a kind of political grouping for which there is no evidence in Rome, but simply allude to a recognizable, if statistically quite rare, type of senator whose activities are scattered sporadically across late-Republic history[.] [...] The 'life-long' popularis [...] was a new and worrying phenomenon at the time of Julius Caesar's consulship of 59: an underlying reason why the man inspired such profound fears.
This summarizes the dominant interpretation of the Populares in 20th-century scholarship, deriving in large part from Ronald Syme in the Anglophone literature. In the early 21st century and as early as the publication of the ninth volume of The Cambridge Ancient History in 1994, the validity of examining Popularist ideology in the context of Roman political philosophy has been reasserted. In particular, T. P. Wiseman has rehabilitated the use of the word "party" to describe the political opposition between Optimates and Populares, based on Latin usage (partes) and pointing to the consistency of a sort of party platform based on the food supply and general welfare of the populus ("people"), making land available to those outside the senatorial elite and debt relief.
- Gnaeus Octavius - Ancestor of emperor Augustus. A conservative member of the Senate that opposed Populares' reforms.
- Marcus Octavius - Ancestor of emperor Augustus. A major rival of Tiberius Gracchus.
- Gnaeus Pompeius Strabo - Father of the famous general Pompey Magnus.
- Gnaeus Pompeius Magnus - One of Sulla's major commanders. Later became the leader of the Optimates in the civil war against Julius Caesar.
- Cato the Younger - One of Caesar's major opponents. Known for his stubborness and immunity to bribes.
- Marcus Licinus Crassus - The richest in Rome. One of Sulla's close associates.
- Lucius Cornelius Sulla - The dictator of Rome. Marched into Rome and killed all his political opponents.
- Marcus Junius Brutus - Assassin of Julius Caesar.
- Cassius Longinus - Assassin of Julius Caesar.
- Decimus Junius Brutus - Originally a supporter of Populares, but later sided with Optimates and assassinated Julius Caesar.
- Scipio Nasica Serapio - Murdered Tiberius Gracchus.
- Cicero - A famous orator.
- Titus Annius Milo - Rival of Publius Clodius Pulcher.
- The Caecilii Metelli - One of the most powerful families in the Roman Republic. A strong supporters of the Optimates.
- Lucius Licinius Lucullus - One of Sulla's major supporters.
- Lucius Opimius - Executed 3000 supporters of Gaius Gracchus.
- Titus Labienus - Originally a supporter of Julius Caesar, but later went over to the Optimates.
- Marcus Porcius Cato (son of Cato the Younger) - Fought against Caesar in the civil war. Later fought and died in Battle of Philippi.
- Marcus Calpurnius Bibulus - Opponent of Caesar.
- Everitt, Anthony (30 November 2001). Cicero: The Life and Times of Rome's Greatest Politician. Random House Publishing Group. p. 400. ISBN 9781588360342.
- Sandys, John Edwin (1921). A Companion to Latin Studies (3 ed.). Cambridge: Cambridge University Press. p. 125.
133[:] Tribute of Ti. Gracchus, his 'lex agraria' and destruction by a rabble of optimates, headed by P. Scipio Nasica [...].
- Morstein-Marx, Robert (5 February 2004). Mass Oratory and Political Power in the Late Roman Republic. Cambridge University Press. pp. 204–205. doi:10.1017/CBO9780511482878. ISBN 9781139449878.
- Andrew Lintott. "Political History, 146–96 B.C." in The Cambridge Ancient History (Cambridge University Press, 1994). p. 52.
- Though this has been a strand in Wiseman's scholarship over the decades, see particularly the introduction and "Roman History and the Ideological Vacuum" in Remembering the Roman People: Essays on Late-Republican Politics and Literature (Oxford University Press, 2009) at p. 14 for partes and "party". A less truncated version of "Roman History and the Ideological Vacuum" may be found in Classics in Progress (Oxford University Press, 2006), p. 285.
- Parenti, Michael. The Assassination of Julius Caesar: A People's History of Ancient Rome. The New Press, 2003. ISBN 1-56584-797-0.
- Videos of talks by Michael Parenti about his book The Assassination of Julius Caesar: A People's History of Ancient Rome, which describes the conflict between Optimates and Populares, in a 76-minute talk (in one part and in eight parts).