Well, it depends on the level of support it gets. If it passes, and Americans show increased support for the effort, it will gain support. A presidential veto

Well, it depends on the level of support it gets. If it passes, and Americans show increased support for the effort, it will gain support. A presidential veto could potentially energize this support (granted, it could also kill it). If Americans make it known that this is a big issue for them, there is a chance it could get enough support to override the veto (I'm assuming there are a few Republicans who support PRISM that would vote to override the veto just to knock Obama around a bit).