If Caesar was negotiating in bad faith (which I am not entirely willing to concede), it may be simplay that he was responding in kind. He had no reason to believe that the boni were negotiating in good faith either. Certainly, Pompey seemed to be negotiating honestly, but Caesar had to be aware of the growing division between them and one has to wonder at the value of Pompey’s offers when Cato & Co. were out there making threats and calling for the destruction of Caesar’s career.

Did Caesar fear losing the election? There was always a risk of political shenanigans twisting the outcome of the election. But far greater was the risk of no election at all or Caesar being somehow shut out of any election. Trials, too, could be fixed no matter how much Caesar spent on bribes. But even if he won any trial, the loss of consular immunity left him at risk. Roman politics was always rough and tumble and had become far more so in the previous few decades. While Caesar was consul or held the imperium, he had not only illegal immunity, but a degree of religious inviolability. To physically attack or instigate an attack on such a person was an act of impiety and sacrilege. Cato, for all his hostility and malevolence, was enough of a prig and a prude to be held back be such considerations.

As for rumors of Caesar planning to march on Rome appearing as early as 50 or 51, that need not mean very much. Charges like that had become relatively common since the wars of Marius and Sulla; they were no less facile than charges of Medizing in fifth century Greece or plotting a helot uprising in Sparta. It was easy to claim and a surefire way of spinning public opinion against someone. There didn’t have to be any basis in fact.

I suppose Caesar did have a hand in destroying the Republic, but it was Cato who put him in the position of doing so. Had Caesar been granted the rights and privileges due any other patrician, he would never have marched. But his popular politics and skill at wielding political power were just too much for Cato, who decided that for the good of the Republic (or at least the power of the “better” people in it), Caesar could not be given his rights. Caesar may have been the instrument, but Cato pulled the trigger.