The FTC's most recent policy guidance is a helpful compilation covering its modern history of vertical merger enforcement, with links to all of its precedent. See, https://www.ftc.gov/news-events/press-releases/2020/12/ftc-issues-commentary-vertical-merger-enforcement
The Commission split 3-2 on partisan lines to issue the commentary, reflecting the same split on issuing the Vertical Merger Guidelines themselves. The quote below shows two members of the FTC's majority growing frustrated with their colleagues who seem to make generally disapproving noises about without suggesting how they would overcome the existing caselaw and challenges of litigating in the face of evolving economic theory.
Watch this space in the coming months, this could get interesting when President Biden appoints a new FTC Chair, and potentially a new democratic Commissioner which would change the partisan balance of power. The Commission traditionally has not been a partisan organization, we'll see if it remains so.