Now in a graphic view:
Basically, Vettel's streak of good results is ejecting everyone out of the Comfortable zone. Now every contender has a difficult task to catch Vettel.
Very soon, some theoretical contenders will be out of the realistic zone, i.e. they will be practically discarded for the title.
In a short term, only Alonso and Kimi could mount a reasonable challenge to SV's expectations. In mid term, perhaps Hamilton could do it (if Mercedes gets a string of great results and Red Bull fades out).