Denver liked James when he was a free agent in 2006 before he signed with the Cardinals. The team thought he would be a good fit for its zone-blocking scheme. Coupled with the Broncos' previous interest and the fact James would fit is that Denver has a need at running back.
The Broncos are on their fifth tailback because of injuries. Denver is using rookie fullback Peyton Hillis at tailback along with newly signed Tatum Bell, who was working at a Denver-area cell phone shop prior to signing last week. The Broncos feel like they can survive with Hillis and Bell (Selvin Young is trying to return from a groin injury he suffered seven weeks ago).
Still, if a reliable veteran tailback such as James became free, Denver would surely consider signing him for the stretch run. James wants out of Arizona because he has lost his playing time.
Arizona has been reluctant to accommodate him and it is highly unlikely it will change its mind. The Cardinals don't want James to go help another team it could meet down the road this season.
The Cardinals, though, will very likely part ways with James in the offseason. Would Denver be interested then? Well, the Broncos are always interested in running backs and it could look at James. But there is urgency now in Denver.
Denver could have other designs at the position in the offseason. The best bet for James landing in Denver would be now. He'd probability love it.
The problem is the Cardinals control the situation and James is likely not going anywhere right now.