Marius, title character and hero of First Man in Rome is, for the most part, not portrayed as any sort of radical, but simply as a successful general seeking to improve his army and only seeming radical because of far-ranging and unanticipated impacts from his military reforms.
The novel also does a good job of showing that there are two things you never want to see made, laws and sausages.* Admittedly, it can be very hard from our vantage to distinguish what in Rome was considered sausage making as usual, what was constitutional hardball, and what is flat-out unconstitutional. It can even be difficult to distinguish these things in our own society, where we know the rules much better and have an actual written constitution, which Rome did not.** Claiming to hear thunder or that the auspices are otherwise unfavorable sounds very much like sausage making as usual. Requiring every Senator to take an oath to uphold Marius' land bill or be banished is hardball, although probably necessary to keep the measure from being undone. Mob violence is clearly unconstitutional, although even it can be grudgingly justified in extreme cases of the the Senate protecting its own for their most egregious conduct. Other cases are less clear to the modern reader.
But even if Marius was mostly just a general wanting to improve his army, and even if his political tactics were usually no worse than sausage making as usual, with a little hardball thrown in, on one issue at least Marius was a genuine radical -- the expansion of Roman citizenship to the Italian allies. Italy of Marius' time was completely under the sway of Rome, with its residents divided into three categories. Roman citizens had various rights and privileges (not made altogether clear in the novel, although they included the right to be free of flogging and other corporal punishment, the right not to be enslaved for debt, and the right to participate in the political system). Within these citizens was the social, if not necessarily legal, distinction between a Roman of the Romans (i.e., an old Roman citizen descended from the original Romans) and a late comer. Marius was such a late comer. Other allies had the Latin rights,*** allowing them most of the private rights of a Roman citizen, but not the right to vote, hold office, or sit on juries. Pressure was growing among the Italian allies for Roman citizenship. Marius extended citizenship to Italians who fought in his armies and made various other extensions on a limited and provisional basis. But in private, he made no secret that he wanted to extend Roman citizenship to all the Italian allies.
This appears to be historically accurate, and it is part of a consistent pattern. In general, among Roman politicians, favoring loci of power outside the Senate, championship of the poorer Romans, and the wish to expand citizenship tended to correlate. This pattern held consistently, through the Gracchi, to Marius, to Caesar. This is convenient, I suppose, for people who like to evaluate politicians on a linear right-left spectrum. It is less convenient for people like me who expect populist politicians not to fit very well on the left-right spectrum, and to punch up and kick down at the same time. It is particularly inconvenient for me since I suspect right wing populism to be a particularly toxic ingredient in the failure of democracy. Perhaps I should amend that and see if it is perhaps a difference between the failure of modern democracy and such failures in classical times. Right wing populism simply does not appear to have been a factor in ancient Rome (or Greece, as far as I can tell). It is also surprising because kicking down sells, whether in Classical times or in modern times. The Gracchi brothers cost themselves considerable popular support with their insistence on expanding citizenship. Rome's poor liked the exclusiveness of their citizenship and were not eager to share it with outsiders. Nor was the issue solely one of psychology. The Roman poor were quite eager to accept land taken from Italians, rich or poor. It would have been an easy matter for the Gracchi to do just that, and to acquire a considerable popular following as a result. But the Gracchi were "pure" left wing populists who refused to advance on group of have-not's at the expense of another, to their own expense.
Although McCullough does not dwell on the matter, one can imagine Marius having similar problems with his soldiers. McCullough portrays him (presumably accurately) as immensely popular with his troops, and with good reasons. He took an unemployed, impoverished, despised rabble and offered them employment, structure, self-respect and prestige as soldiers. He is a brilliant general who wins glorious battles with minimal casualties, while his incompetent rivals keep getting their armies wiped out. (I have to think that would make him very popular indeed!) And he offers them a generous share of the spoils, and the prospect of land. But, on the other hand, he is taking away the once source of prestige and self-respect his head count soldiers had before -- that they were Roman citizens, and that many were "Romans of the Romans," i.e., descended from old Roman stock. The general offering them all these things was a citizen, but not a "Roman of the Romans." Perhaps some of Rome's lowest, poorest, and most degraded citizens might nonetheless consider themselves superior to him in pedigree. And he wanted to raise mere Italians to citizenship and perhaps even to equality. It would all be a matter of whether the new source of self-respect Marius had to offer outweighed the old source that he was undermining, whether to the Head Count living in a cardboard box and cooking sparrows on a curtain rod, but having the satisfaction of knowing the mere Italian in the next box doesn't even have sparrows or a curtain rod is preferable to moving to better quarters but having to share them with an Italian.
The novel also does a good job of showing the Law of Unintended Consequences at work, and why seemingly modest reforms can be more radical than anyone suspects. After seeing yet another army wiped out by incompetence and Rome exposed to possible German invasion, Marius turns to the property-less Italian Head Count for his next recruits. The Italians say they have no property-less men; they have all been reduced to slavery by debt. Marius, moved partly by the desire for more soldiers and partly by a sense of the injustice to the Italians, calls for the freeing of all Italian debt slaves. Of course, no ancient Roman would ever think to question the legitimacy of slavery itself, only its application to fellow Italians. But it turns out that the non-Italian slaves are mightily resentful that their Italian fellow sufferers are to be released, while they are not. In Sicily, a great grain basket for Rome, about a quarter of all slaves are Italians. Their owners naturally resist, and the non-Italian slaves revolt. And let no one romanticize a slave rebellion. One can happily acknowledge the injustice of slavery (and, indeed, the lot of a common Roman field slave appears to have been a brutal one) and at the same time acknowledge that slave rebellions are mad frenzies of destruction and atrocity -- on both sides. Marius never for one moment disputes the common view of the revolt -- it is a destructive business to be put down.
But here was also see how people can be radicalized by events. Consider the case of Marcus Livius Drusus. Son of a prominent conservative politician who dies at the beginning of the book, Drusus appears to have at least some liberal tendencies, as we first meet him as a young lawyer passionately defending and Italian facing flogging and possible enslavement for debt. Drusus argues that since the Italian has agreed to pay his debt, it is unfair that he should be ruined just because he happens not to hold Roman citizenship. He nonetheless shows his allegiance to the old order by marrying the daughter of Quintus Servilius Caepio and forcing his sister, on pain of being locked up in her room for life, to marry his son. However, he fights at the Battle of Arausio, were the Roman army was destroyed because of his father-in-law's insubordinate conduct, and himself survives only because he is knocked unconscious and left for dead when the Germans come by to kill off the Roman survivors. When he recovers, he saves the life of the Italian Quintus Poppaedius Silo by pulling him out from under a pile of dead men, where he has gone unnoticed. Silo, in turn, (probably) saves Drusus' life by draining a wound that was well on the way to killing him. (Quintus Servilius Caepio, Jr. is also present at the battle, but on the edge and runs away. He then heads back to Rome with his father, without making any attempt to offer aid to any possible survivors). And Drusus discovers that Silo, as a mere Italian, had no idea that so many lives were thrown away because of a ridiculous dispute between the Roman commanders and is justifiably outraged. Drusus grudgingly supports Marius and his military reforms, despite still regarding him as a dangerous radical. Yet by the time of the Sicilian slave revolt, Drusus is sounding more radical than Marius, regarding the slaughter of so many, Italians as well as non-Italians, as a shocking atrocity and blaming it all on self-serving politicians.****
But presumably the one who will be radicalized most is Marius himself. We end the novel with him showing himself a true son of the Republic and joining forces with conservative politicians when a real demagogue starts to threaten it. Yet as a matter of public record, he ended up going off the deep end and festooning the walls of Rome with the heads of his enemies. How this happened will presumably transpire in the next book.
And then there is the matter of Lucius Cornelius Sulla, Marius' friend and colleague, later to become bitter enemy. Though they remain close friends and allies throughout the novel, subtle signs of their impending breach are there. Marius does horrible things sometimes, but no more so than is inherent in the nature of war at the time. Sulla shows (purely fictitious) streak of gratuitous sadism. They have little ideological differences. Sulla, though initially poor as Rome's poorest rabble, dissolute, and bisexual, has a fine patrician pedigree and is sensitive to some of the traditions Marius is violating. In particular, he shares the conservatives' blood-and-soil view of Romaness and their horror at the though of assimilating far-flung portions of the empire to it. And, when rabble-rousers start a revolt against the Republic Marius merely joins forces with conservative politicians to lawfully put it down. Sulla starts directing a group of young, right-wing aristocrats who think the law is too easy and want to take matters into their own hands. Marius does not know about these activities, and would certainly be furious if he did know.
But in the end, I cannot believe that their breach will be over ideology. It looks to be more a contest of raw power, a case of "this town ain't big enough for the both of us." And (if rumor is correct), Marius will be more to blame for their breach than Sulla. I can also confidently say that, while Sulla may turn out to be a right winger (and that is far from clear at the end of the novel) he is definitely not a conservative. He is simply too estranged from the established order ever to be a part of it. What remains to be seen is whether he is a sparrow hawk. What is a sparrow hawk? It is a concept I learned in an essay about 1960's radicalism. The essay both condemns 1960's radicals and warns that they are not a true threat and that overreaction to them will be dangerous. And it illustrates the danger in the Parable of the Pigeons. When the Victorians built the Crystal Palace museum, they encased some trees in it, along with the pigeons in the trees. Soon pigeon droppings were ruining everything, but how to get rid of the pigeons? Shooting was out of the question because it would destroy the glass panels. What alternatives were there? The Duke of Wellington recommended sparrow hawks. Not addressed -- how to get rid of the sparrow hawks once they got rid of the pigeons. Says the author of the essay, "Before the Right has recourse to hawks, it had better solve the problem of how to get rid of them. In the 1930's the German Right failed tragically to solve that problem." I look forward to seeing whether something similar plays out with Roman conservatives and Sulla.
*This may be an older metaphor than we realize. Aristophanes portrays politicians as sausage makers in his play Knights.
**This is significant, I think, for instance, when one reads Plutarch's biography of Cato the Younger, of whom he is a fan. Invariably he portrays Cato's opponents as fighting dirty and Cato as heroic. The novel is useful as showing to what extent the tactics of Cato's opponents, though not very nice, were by no means unprecedented, and the extent to which not everything Cato did was so nice either.
***NOT to be confused with the Latin Rite!
****And Young Caepio finds all of this so incomprehensible that he can only attribute it to Drusus being hit over the head in the fighting and suffering some sort of brain injury. I know I consider elites obtuse, but surely not THAT obtuse!