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.