In 1984, what are some of the characteristics of the proles that, in Winston's eyes, make them the ultimate means for overthrowing Big Brother?

For one, there are many of them.  They live freely in their own area of town where they laugh and sing and talk without fear.  They are able to plan a rebellion without fear of the telescreen hearing or seeing them...they are not under the same rules as the Party members.  However, what Winston does not see is that the Proles, although they are kept in relative poverty, are not unhappy with their lives.  It is only the Party members who live under such scrutiny who dream of rebellion and hope the Proles will come through for them.  The Proles have the numbers, but the motive is not there for them as it is with the Party members.  Likewise, the disgruntled Party members have the motive but not the numbers.  It is a horrible catch-22.  Unless a group of disgruntled Party members can sneak away from the ever watchful eye of Big Brother long enough to lead the Proles to rebellion, it will never happen.