Monday's revelation that progressive as well as conservative groups seeking tax-exempt status had been singled out for review by the Internal Revenue Service left one pressing question: Why did the inspector general's report detailing improper scrutiny only mention conservative groups?

Last night we got the answer: The IG only reported on conservative groups because that's what Rep. Darrell Issa (R-CA), the notoriously partisan chairman of the House Oversight Committee, told him to do. Via The Hill:

The Treasury inspector general whose report helped drive the IRS targeting controversy says it limited its examination to conservative groups because of a request from House Republicans.

A spokesman for Russell George, Treasury's inspector general for tax administration, said they were asked - by House Oversight Chairman Darrell Issa (R-Calif.) - "to narrowly focus on Tea Party organizations.

The inspector general's audit found that groups seeking tax-exempt status with “Tea Party” and “patriots” in their name did receive extra attention from the IRS, with some facing years of delay and inappropriate questions from the agency.

Note that this explanation is inconsistent with the description of their investigation the IG gave in its May 14 report, which strongly suggested that they had reviewed IRS targeting of all groups that sought tax-exempt status:

WHY TIGTA DID THE AUDIT

TIGTA initiated this audit based on concerns expressed by members of Congress. The overall objective of this audit was to determine whether allegations were founded that the IRS: 1) targeted specific groups applying for tax-exempt status, 2) delayed processing of targeted groups' applications, and 2) requested unnecessary information from targeted groups.

What all of this means is that Issa took the media for a ride. Again. 

Recall Washington Post reporter Ezra Klein's explanation for what made the IRS activity detailed in the IG report scandalous:

Here's what everyone agrees on: The Determinations Unit based out of the Cincinnati IRS targeted 501(c)(4) applications that used tea party-related terms for extra scrutiny. Whether the intent was benign, as the IRS swears, or rogue agents were carrying out a political vendetta, the effect was to politicize the IRS's filtering process. That's a huge problem.[...]

The problem wasn't that the IRS closely scrutinized questionable applications from tea party groups. It's that they didn't closely scrutinized the applications from other questionable groups as well. The scrutiny was the part they did right. The targeting was the part they did wrong.

Everyone agrees that it's a “huge problem” if the IRS is scrutinizing conservative groups and not progressive groups, which is what the IG report suggested. The right-wing media, with their typical tendency to vastly overreach, claimed absent evidence that the IRS targeting had been directed by the White House or initiated by officials in Washington, D.C. and demanded the appointment of a special prosecutor.

But now reports indicate that "[t]erms including 'Israel,' 'Progressive' and 'Occupy' were used by agency workers to help pick groups for closer examination." And the reason we are only learning about this now is because a Republican member of Congress asked that an investigation only review the targeting of conservative groups, not progressive ones.

This leaves a new question. The revelation of Issa's role in the slanting of the IG report follows months of the California congressman apparently leaking out-of-context statements to credulous media to drum up controversy over both the IRS story and the Obama administration's response to the September attacks on U.S. diplomatic facilities in Benghazi, Libya. Will the media continue to take Issa seriously, or will they begin to treat him as a partisan actor who is using his position to attack the Obama administration rather than seeking legitimate investigations?

We'll find out soon. Mere hours after the news broke that the IRS had also targeted liberal groups for scrutiny, Issa's committee announced that it had subpoenaed four State Department witnesses as part of their Benghazi investigation.