Let's not deceive each other. A team can have a good start in a league but stumble towards the end of the season. It happened to Man United some time back. They had a nine point lead with just a few games remaining. Then they started losing consistently and City [I think] dethroned them.
As for Arsenal, I think Wenger was an idiot to lay his job on the line. He said if he won't win a title he'd leave. Fact is [if the West Brom] match is anything to go by, he should start packing his bags because Arsenal most certainly, won't win bag the title this season.