[Raynor]

Originally Posted by MatthewM

or maybe they always had this power

I would say this is the case; concerning the perception of the ring by the nazgul and the recurring motive of barriers, it is stated in Unfinished Tales:

Originally Posted by Hunt for the ring

[Khamul] was well aware that the Ring had crossed the river; but the river was a barrier to his sense of its movement and that the Nazgul would not touch the "Elvish" waters of Baranduin

Originally Posted by Notes to 'Concerning Gandalf, Saruman and the Shire'

Of Khamul it is said here that he was the most ready of all the Nazgul after the Black Captain himself, to perceive the presence of the Ring, but also the one whose power was most confused and diminished by daylight.