In the continuing battle over Republican allegations that the Obama administration pressured the Internal Revenue Service to obstruct Tea Party applications for tax-exempt status, three well-known political figures are among those likely to benefit: Karl Rove and David and Charles Koch.

The story began in 2010, but did not become public until May 10, 2013, when Lois Lerner, then the director of the little-known Cincinnati-based Exempt Organization Division of the I.R.S., which reviews applications for tax-exempt status for nonprofits, publicly acknowledged and apologized for the practice of targeting Tea Party groups for special scrutiny.

Lerner’s admission came four days before J. Russell George, the Treasury department’s inspector general for tax administration, released a critical report confirming that conservative groups had indeed been targeted. Its title presents its conclusion: “Inappropriate Criteria Were Used to Identify Tax-Exempt Applications for Review.”

George and his investigators found that in August 2010, the I.R.S. Exempt Organization Division had distributed to its staff a “Be On the Look Out (BOLO)” warning about groups with the words “Tea Party” in their name. These Tea Party-linked groups were to be subject to detailed examination regarding their eligibility for tax-exempt status. The BOLO directive was later expanded to include organizations that contained the word “patriot” in their names.