Albert Barnes Commentary John 12:42

"Nevertheless even of the rulers many believed on him; but because of the Pharisees they did not confess [it], lest they should be put out of the synagogue:" — John 12:42 (ASV)

The chief rulers. Members of the Sanhedrin — Nicodemus, Joseph, and others like them.

Because of the Pharisees. The Pharisees were a majority of the council.

Put out of the synagogue. Excommunicated. See Barnes on John 9:22-23.