Caesar may not have had reason to fear Pompey directly. He did, however, have plenty of reason to worry about Cato and by 50 Pompey had become the tool of the boni. Never forget that it was Cato who asked many years earlier why no one had killed Caesar. It was Cato who led the effort to give Caesar the worst possible proconsular province, where he would have no chance to cover himself with military glory or to line his pockets (a difficult thing to do considering that was the very purpose of proconsular provinces in the first place). Cato wanted to keep Caesar from getting any province at all, but Pompey prevented that from happening to his then-ally. It was Cato who was making it clear that he was coming after Caesar with everything he could muster: misconduct charges, trials over every single thing that had happened while Caesar was in Gaul.

The senate had granted Caesar the right to run in absentia and maintain his immunity? The senate had been proving for years that they were more than willing to ignore, violate or overturn any law that they found inconvenient. Promises to Caesar—even without Pompey’s “forgetfulness”—could be set aside in a heartbeat. And if he somehow managed to become consul anyway, then Cato was willing to bide his time. And I believe that Caesar firmly believed that Cato could and would use Pompey and his armies against him if necessary.

Now from our perspective the business of having Curio constantly harping on the dangers of Pompey’s armies may look suspect. Caesar had been related by marriage to both Marius and Cinna who used their military powers to seize control. OTOH, Pompey had been a protégé of Sulla’s and his father would have marched on Rome had he not died suddenly. Given the events of the last century, the senate was more than a little paranoid about this sort of thing. If nothing else, the constant reminder that Pompey could bring men under arms against Rome had to make the boni a little less willing to grasp that weapon. It may have been what kept the civil war from being fought in Gaul or northern Italy.

(PS. I know I'm way behind here, but my deadline is this week and I hope to catch up by next weekend.)