He was a spiritual mentor to Luther, but never joined Luther's movement. He was accused of Lutheranism, but abjured this (though he refused to revoke any Lutheranism on the grounds that he had never held it). The Catholic Encyclopedia (1913) insists that "Staupitz was no Lutheran but thoroughly Catholic in matters of faith."
What is particularly interesting to note for those interested in the issue of Calvinism is that Staupitz held to Limited Atonement. David Curtis Steinmetz reports:
The death of Christ is sufficient as a sacrifice to atone for the sins of all men. The mere fact that baptized infants may be saved without any merits of their own is in itself evidence adequate to establish the sufficiency of the atoning death of Christ. This sufficiency, however, is not unlimited. The limitations are twofold.(D.C. Steinmetz, Misericordia Dei: The theology of Johannes von Staupitz in its late medieval setting, (Brill: 1968) pp. 144-45)
On the one hand, the atonement is limited in its effect to the remission of the sins of the elect. Christ did not lay down his life for all men, Staupitz noted, but only for many (non pro omnibus sed pro multis). Staupitz did not believe that the atonement was inherently inadequate to expiate the sins of the whole world, but rather that it was not intended to do so. It is not a question of inadequacy, but of intention. The atonement is delimited and defined by divine election.
He also limited the atonement in another way, but it is this primary way that is of interest to the Reformed reader who might be mislead by folks who suggest that Calvin innovated limited atonement. It was not something Calvin invented, and it was not something that Luther invented. It is something that Scripture teaches, and it is something that many folks who have professed faith in Christ have taught throughout history.
Furthermore, it is the other limitation on the atonement, to make remove for Penance, that the first generation Reformers had to so vociferously dispute from Scripture, occasionally leading to unguarded quotations that our Amyraldian friends enjoy mining and presenting outside the historical context in which they were made.
Is Staupitz representative of the views of theologically-inclined churchmen (don't think that such a statement is redundant especially in the late medieval period) just before Luther? Hard to say. I have not seen enough data to come to a firm conclusion. Nevertheless, his comments do suggest that there is a reason that the first generation of Reformers did not face opposition on the doctrine of limited atonement: it was already part of the theological milieu, not to mention (of course) that is the clear teaching of Scripture.