Public data from the Internal Revenue Service, which recently acknowledged that agency officials singled out conservative groups for special scrutiny, shows that dozens of Tea Party groups were approved for tax exempt status beginning in May 2012. That was the same month that Representative Dave Camp of Michigan wrote to the I.R.S. asking for information about all “social welfare” groups that had applied for tax-exempt status in 2010 and 2011, to determine whether the I.R.S. was targeting conservative groups.

The flurry of approvals that came in the next few months was a sharp break from the previous two years, during which the agency approved just a handful of 501(c)(4) applications from Tea Party groups.

The public data provided by the I.R.S. does not include information on when groups submitted their applications for tax-exempt status, or how long they waited compared to the average application.

But an inspector general’s report indicated that I.R.S. officials began targeting conservative groups in March 2010 by searching for groups with names containing “Tea Party,” “patriot” or “9/12.” The report says officials then switched to more expansive, less partisan search criteria in July 2011 and in January 2012, before broadening the criteria a third time on May 17, two weeks after Mr. Camp’s letter.

But the first two revisions to the search criteria do not appear to have resulted in more Tea Party groups gaining approval. During the entire two-year span — from March 2010, when the agency began singling out conservative groups, to April 2012, just before it received Mr. Camp’s letter and changed its search criteria for the last time — the I.R.S. approved the applications of just four groups with those conservative keywords in their names. After the I.R.S. altered its search criteria the final time, the agency approved more than 40 Tea Party applications.

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According to the I.R.S. records, 54 organizations were granted 501(c)(4) status since 2010 with “Tea Party,” “patriot” or “9/12″ in their names. Five of those groups were approved in the first three months of 2010. Approvals then slowed considerably, I.R.S. data shows.

The Indiana Armstrong Patriots was the only Tea Party organization approved during all of 2011, and it was one of just four groups with “Tea Party,” “patriot” or “9/12″ in their names that were approved from April 2010 through April 2012.

The I.R.S. then approved 45 Tea Party groups in just 11 months, from May 2012 to March 2013. About half of those approvals — 23 — came in June, July and August, the first three full months after the final revision of the search criteria.

As a point of comparison, we tried to identify liberal groups approved for 501(c)(4) status since 2010. A search for “progress,” “progressive,” “liberal” and “equality” finds 32 groups. (This might not be a representative sample — identifying left-leaning groups is more difficult, as there are is no clearly defined nomenclature on the left equivalent to the Tea Party.) The I.R.S. approved these groups at a fairly steady rate from 2010 through 2012. The I.R.S. approved 13 in 2010, nine in 2011 and 10 in 2012.