Lois G. Lerner and her subordinates do some of the most sensitive work at the Internal Revenue Service. They oversee politically active nonprofit groups — whose politicking often tiptoes to the edge of what a nonprofit is legally allowed to do.

That task requires agents to know politics. But they can’t show even a hint of partisan bias.

So Lerner tells them: Don’t do anything you wouldn’t want to explain to Congress.

“Think about [if] you’re in the spotlight, before a congressional committee, and they’re asking you, ‘Why did you do it?’ ” said Marvin Friedlander, a retired subordinate, repeating what he’d heard Lerner say. “If you can explain that, fine. . . . If you don’t have a good explanation, then you need to think a little bit about this.”

Today, the spotlight is on Lerner. And it is not going well.

A report due this week says the IRS targeted groups with names containing “tea party” and “patriot.”

Lerner, director of the IRS’s exempt-organi­zations division, let slip last week that low-level IRS staffers had focused extra scrutiny on conservative groups with words such as “tea party” or “patriot” in their names. Since then, internal reviews have shown that Lerner knew about the targeting in 2011 — but neither Congress nor the public knew until Friday.

In interviews Monday, even Lerner’s critics said she had done her job without showing a political bent.

In fact, many thought she had gone too easy on some conservative groups. That reputation is now being called into question with the revelations of one disastrous day.

“If anything, my critique of her was that she wasn’t aggressive enough,” said Paul Streckfus, who edits a newsletter devoted to tax-exempt organizations. “Which is rather ironic.”

Lerner, 62, did not respond Monday to a request for an interview made through an IRS spokesman. Last week, she became the face of a scandal that has put the Obama administration on the defensive.

On a conference call with reporters, organized so she could explain her unexpected revelation of the targeted scrutiny for conservative groups, Lerner said that she was “not good at math” when asked to quantify the scope of the targeting. (She is a lawyer by training, not an accountant.) Lerner apologized for the focus on conservative groups but did not say whether any IRS employees had been disciplined for their role in it.

Official investigations have shown that Lerner was told of the extra scrutiny for “tea party” and “patriot” groups in late June 2011. The groups were applying for tax-exempt status as “social welfare” groups. She objected to the criteria being used and on Friday described it as a misguided effort to deal with a deluge of applications for tax-exempt status.

But it was not until May 2012 that the standards for targeting became more general, looking for groups with any kind of heavy political activity regardless of political leaning.

In March 2012, IRS Commissioner Douglas H. Shulman told a congressional oversight committee that there was no targeting of conservative organizations. IRS officials have not said whether Lerner discussed the previous targeting with Shulman before his congressional testimony.

The result, however, ran squarely against a value that Lerner had been preaching for years: openness.

“I continue to believe that dialogue between the regulator and the regulated provides the best vehicle for enhancing our understanding of one another,” Lerner said in a speech at the Georgetown University law school last month.

Lerner is a registered Democrat, records show. But she is a career federal worker, not a political appointee. Lerner has been a government lawyer since at least 1981, having worked for the Justice Department and the Federal Election Commission before joining the IRS in 2001. Outside of work, she volunteers as a rescuer of pets, including some left helpless after Hurricane Katrina.

Lerner has headed the IRS exempt-organizations office since 2006. It oversees the familiar kinds of nonprofits — universities, hospitals, charities — as well as the murkier world of “social welfare” groups that also dabble in politics.

These groups, known by the legal designation 501(c)(4), can avoid paying taxes as long as politics does not become their “primary purpose.”

The job for Lerner’s office is to decide how much politics is too much.

“It’s a difficult dance,” said Philip Hackney, a former IRS lawyer who teaches law at Louisiana State University. IRS examiners often ask about how much money and time a particular group spends on political purposes — and how much it spends on everything else.

Hackney said Lerner often reminded staffers that they could not make decisions based on a group’s political beliefs. “She would regularly be working with those folks to train them to be thinking in that sort of nonpartisan manner,” he said.

During Lerner’s tenure, one of the touchiest questions was how to deal with churches that preached politics from the pulpit. After the 2004 elections, there were complaints that conservative pastors had endorsed President George W. Bush’s reelection — something they were barred from doing at churches treated as legal nonprofits.

The IRS found that some churches had indeed overstepped the rules. But the people who made those charges said that, under Lerner, the agency was too timid in following up.

Barry Lynn of Americans United for Separation of Church and State said he was surprised to hear that, under Lerner, the IRS had targeted another group of conservative organizations.

Instead of churches that already had tax-exempt status, this time it was tea-party-affiliated groups that were applying for that status.

“This whole thing strikes me as two wrongs not making a right,” Lynn said. “Just making two wrongs.”

Josh Hicks and Julie Tate contributed to this report.

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