It is thought so by some highly educated people. You will have to do your own research on this. But to answer your question: his earlier Epistles contain many Gnostic words and phrases. His later works don't but are probably forgeries. Fingers point at +Irenaeus.
One thing you will have to understand is that the Church needed a way out, because it was dying quickly in Israel. +Peter came back from preaching to the Jews, which was a complete failure. Even basic knowledge of Judaism would make you understand why (for starters, Jews do not believe man needs grace to be righteous).
It was +Paul who had the flexibility needed to make Christianity acceptable to Gentiles. He even reprimanded +Peter publicly for his resistance to change Judaic practices or to eat with Gentiles. Without +Paul, Christianity would bee a dead religion.
To help you down the path of research in finding these highly educated people, Doc, the best place to start is with the primary proponent of the idea of Pauline Gnosticism: Elaine Pagels.
'Nuff said.