This paper centers on the nature of clitic doubling in River Plate Spanish. We present some novel empirical observations regarding clitic doubling and its relation with extraction and ellipsis. Concretely, we show that clitic doubling ameliorates some island effects. However, this repair effect disappears under ellipsis. We claim that this anti-repair effect follows if clitic doubling is a PF operation (in the sense of Distributed Morphology) that is blocked under ellipsis. Crucially, anti-repair effects are not observed in contexts of clitic left dislocation. We propose then that this is because clitic left dislocation is a purely syntactic phenomenon and, as expected, is not affected by ellipsis. One important consequence that follows from our analysis is that Kayne’s Generalization (i.e. the fact that clitic doubling is dependent on differential object marking) has to be seen as a purely PF-phenomenon, an idea in consonance with Bobaljik’s (2008) recent findings on the relation between case and agreement. Keywords: clitic doubling; focus fronting; island repair; ellipsis; PF-resumption