The problem with speculating as to whether Bachmann or Newt or Palin etc. will split Paul's vote is, it isn't clear Paul is really going for a vote that can be split. His pro-constitution supporters (us) are rather locked in solid behind Paul, so the actual voting bloc that means something is the religious right and social/cultural conservatives. Paul has never reached out strongly to get this faction, even though he's got the ammo (pro-life doctor, supported DOMA, Christian, pro gun rights, anti-amnesty).
Yes, they are wary of Paul due to the war/drug issues, but that gap is bridgeable if he emphasizes the above ammo. Not working to get this gettable vote means allowing it to become a jump ball for other contenders to get. One of the statist candidates will end up with the lion's share of these people, not because they are out to 'split' Ron's support, but because he never went for them in the first place.