Full Idea
The property of 'possibly being a Republican' is as much a property of Bill Clinton as is 'being a democrat'. So we don't peel off his properties from world to world. Hence the bundle theory fits our treatment of objects better than bare particulars.
Gist of Idea
Objects retain their possible properties across worlds, so a bundle theory of them seems best
Source
M Fitting/R Mendelsohn (First-Order Modal Logic [1998], 7.3)
Book Reference
Fitting,M/Mendelsohn,R: 'First-Order Modal Logic' [Synthese 1998], p.148
A Reaction
This bundle theory is better described in recent parlance as the 'modal profile'. I am reluctant to talk of a modal truth about something as one of its 'properties'. An objects, then, is a bundle of truths?