This was somewhat early in the empire though and had some ridiculous heights. At one point the Praetorian guard (the emperors personal army within Rome) auction

This was somewhat early in the empire though and had some ridiculous heights. At one point the Praetorian guard (the emperors personal army within Rome) auctioned off their support and caused absolute havok in what is called 'the year of the 4 emperors' (I think this is the same point in time, it's been a while since I've read about it). However their power diminished a lot as the empire grew and Rome became less relevant. Eventually emperors began to not even visit Rome at all during their lives, and the power of the guard faded to nothing. At the time I was commenting about they had next to no influence, much like the senate.