If anyone is overperforming in the Fox polls, it's Jeb Bush. Some of the variations between different polls can be attributed to different ratios of republicans and republican-leaning-independents. Wording of the questions are different from poll to poll, the easiest way to see this variation is the number of people who are undecided. Most is due to margin of error. For most of these polls the margin is about 5%. So if you're down for instance 3% in the poll you are statistically tied for the lead.
The trend though is that Walker is down in the polls, Rand Paul is up a couple of points, Huckabee has a small announcement bump, Carson is doing well, while Bush and Rubio are holding on after previously sinking in the polls. Cruz is fading a bit, but not much.
The most usual polls at this time shows Paul, Bush, Rubio, Cruz, Carson, Huckabee and Walker with 65-70% almost equally divided between them. Then about 15% undecided, and the remaining 15-20% divided among the "Clowns and unknowns"-caucus. (Perry, Christie, Santorum, Trump, Fiorina, Graham, Kasich, Jindal, Pataki) At this point, considering the strong frontrunners, the rise of these remaining candidates will depend on the major candidates stumbling. If Bush is fading, then Christie or Kasich can take his place, if Huckabee or Carson gives up, it will give room to Santorum etc.
