Murky
Deity
The populares weren't a coherent political faction, it just meant a member of the senatorial class who appealed to the plebeians. It was a matter of political strategy, not of principle, and plenty of senators moved back and forth between each camp at will. You really can't paint them as some sort of Classical equivalent to the Jacobins.
It's more complicated than that. Julius Caesar was not the equivalent of a modern leftist. He was elitist, but at the same time he was on the side of egalitarianism. His reforms helped the plebeians at the expense of the rich.
Brutus wasn't some heroic defender of the Republic. He was out to protect his own wealth and status in the Roman oligarchy.