On Wednesday, the cable news channel suspended two paid contributors, Newt Gingrich and Rick Santorum, who are both weighing presidential bids.While the channel’s move seems pre-emptive — Mr. Gingrich is expected to signal his intentions on Thursday — it still leaves Fox with three other potential candidates: Sarah Palin, Mike Huckabee and John Bolton. But those three, according to Fox, have not shown serious intentions to set up presidential exploratory committees.