The question of how Jesus was treated by the first century believers is, has been, and probably will be, an issue of contentious discussion. Two recent books address the issue, Ehrman's How Jesus became God, and an evangelical response volume, "How God became Jesus".

Personally I think Ehrman's volume has serious flaws, including the fact that he fails to engage certain major authors in this field, including those that I think have it right. These include Larry Hurtado, whose volume Lord Jesus Christ: Devotion to Jesus in Earliest Christianity argues three main theses:

1. Significant devotion to Jesus emerged in the earliest stages of the Christian movement, and was not exclusively a secondary development.
2. The pattern of that development is not easily explainable by analogous phenomenon in comparable groups.
3. The shape of that devotion was offered within an exclusively monotheistic framework, which created a unique phenomenon that could be called binitarian worship.

Ehrman fails to discuss Hurtado at length, and even more puzzlingly fails to discuss or show evidence of having read Bauckhaum, whose book God Crucified, now released as part of an updated volume, Jesus and the God of Israel, argues that the central category for understanding what was going on is to argue that earliest patterns of Christian relationship to Jesus are characterised by including Jesus 'within' the identity of the God of Israel.

On the basis of this work, I think it's right to see that first century believers treated Jesus in a relationship of unity with God the Father, even if the dynamics of that relationship (i.e. a doctrine of the Trinity) did not get fully explored until later centuries. Arguably, there is a proto-doctrine of the Trinity.

However, to give some space to alternate proposals, let me briefly outline a few.

Ehrman's view is that Jesus was an apocalyptic preacher, and that before the New Testament documents final form, there was a shift from seeing him as an exalted, adopted 'god', or intermediary figure, to a pre-existent intermediary (i.e. angelic or similar) figure who became incarnate. So Ehrman's view is still that there was a very important shift very early on.

The view of Bousset, in Kyrios Christos, has until the last 20 years, had significant acceptance. Bousset bassically argued that the Christ cult was a secondary development in a Greek setting, not reflective of early Palestinian/Jewish Christians. In this view, Jesus was seen as a divine 'lord' on analogy with Greek-pagan divine and semi-divine heroes.

Maurice Casey puts this development even later, to the end of the first century and the emergence of Christians in a 'Johannine community', with a majority of Gentile identity.

The concept of 'Messiah' was never equivalent to God, indeed the understanding that the Messiah is 'God' is arguably only a Christian understanding that emerges from the New Testament on the basis of their understanding of who Jesus is and what he does. But if you asked contemporary first-century Jews if the Messiah would be God himself in the flesh, I suggest you would get blank stares.