Washington (CNN)Before Donald Trump and Steve Bannon were enemies, they were allies. And not long before that, Bannon was part of an effort to sink Trump’s presidential hopes — even if Trump didn’t know it.

A conservative watchdog group led by Bannon tried to discredit Trump in the early stages of the 2016 Republican presidential primary by shopping a document alleging that Trump had ties to mobsters, according to conservative sources and a copy of the document reviewed by CNN.

The anti-Trump opposition research was the work of author Peter Schweizer for the Government Accountability Institute, which he cofounded with Bannon in 2012. It described years of alleged business connections between Trump companies and organized crime figures, allegations that have circulated among Trump detractors for years.

The New York Times reported on the document on Friday.