It's the sort of political back-stabbing that defies belief, taking an active role in destroying the Tea Party, which was an authentic grassroots movement of local groups calling for smaller government.  Sure enough, Judicial Watch has found McCain's central role right there in the documents:

Judicial Watch today released newly obtained internal IRS documents, including material revealing that Sen. John McCain's former staff director and chief counsel on the Senate Homeland Security Permanent Subcommittee, Henry Kerner, urged top IRS officials, including then-director of exempt organizations Lois Lerner, to "audit so many that it becomes financially ruinous."  Kerner was appointed by President Trump as Special Counsel for the United States Office of Special Counsel.