Most of the time, an obscure federal investigative unit known as the Office of Special Counsel confines itself to monitoring the activities of relatively low-level government employees, stepping in with reprimands and other routine administrative actions for such offenses as discriminating against military personnel or engaging in prohibited political activities.

But the Office of Special Counsel is preparing to jump into one of the most sensitive and potentially explosive issues in Washington, launching a broad investigation into key elements of the White House political operations that for more than six years have been headed by chief strategist Karl Rove.

The new investigation, which will examine the firing of at least one U.S. attorney, missing White House e-mails, and White House efforts to keep presidential appointees attuned to Republican political priorities, could create a substantial new problem for the Bush White House.

First, the inquiry comes from inside the administration, not from Democrats in Congress. Second, unlike the splintered inquiries being pressed on Capitol Hill, it is expected to be a unified investigation covering many facets of the political operation in which Rove played a leading part.

“We will take the evidence where it leads us,” Scott J. Bloch, head of the Office of Special Counsel and a presidential appointee, said in an interview Monday. “We will not leave any stone unturned.”

Bloch declined to comment on who his investigators would interview, but he said the probe would be independent and uncoordinated with any other agency or government entity.

The decision by Bloch’s office is the latest evidence that Rove’s once-vaunted operations inside the government, which helped the GOP hold the White House and Congress for six years, now threaten to mire the administration in investigations.

The question of improper political influence over government decision-making is at the heart of the controversy over the firing of U.S. attorneys and the ongoing congressional investigation of the special e-mail system installed in the White House and other government offices by the Republican National Committee.

All administrations are political, but this White House has systematically brought electoral concerns to Cabinet agencies in a way unseen previously.

For example, Rove and his top aides met each year with presidential appointees throughout the government, using PowerPoint presentations to review polling data and describe high-priority congressional and other campaigns around the country.

Some officials have said they understood that they were expected to seek opportunities to help Republicans in these races, through federal grants, policy decisions or in other ways.

A former Interior Department official, Wayne R. Smith, who sat through briefings from Rove and his then-deputy Ken Mehlman, said that during President Bush’s first term, he and other appointees were frequently briefed on political priorities.

“We were constantly being reminded about how our decisions could affect electoral results,” Smith said.

“This is a big deal,” Paul C. Light, a New York University expert on the executive branch, said of Bloch’s plan. “It is a significant moment for the administration and Karl Rove. It speaks to the growing sense that there is a nexus at the White House that explains what’s going on in these disparate investigations.”

The 106-person Office of Special Counsel has never conducted such a broad and high-profile inquiry in its history. One of its primary missions has been to enforce the Hatch Act, a law enacted in 1939 to preserve the integrity of the civil service.

Bloch said the new investigation grew from two narrower inquiries his staff had begun in recent weeks.

One involved the fired U.S. attorney from New Mexico, David C. Iglesias.

The other centered on a PowerPoint presentation that a Rove aide, J. Scott Jennings, made at the General Services Administration this year.

That presentation listed recent polls and the outlook for battleground House and Senate races in 2008. After the presentation, GSA Administrator Lorita Doan encouraged agency managers to “support our candidates,” according to half a dozen witnesses. Doan said she could not recall making such comments.

The Los Angeles Times has learned that similar presentations were made by other White House staff members, including Rove, to other Cabinet agencies. During such presentations, employees said they got a not-so-subtle message about helping endangered Republicans.

White House spokesman Scott M. Stanzel said the Hatch Act did not prohibit providing informational briefings to government employees.

Responding to a letter of complaint to the White House from 25 Democratic senators, Stanzel said: “It is entirely appropriate for the president’s staff to provide informational briefings to appointees throughout the federal government about the political landscape in which they implement the president’s policies and priorities.”

However, questions have emerged about the PowerPoint presentations, including whether Doan’s comments crossed the line and whether the presentations violated rules limiting political activity on federal property.

Whether legal or not, the multiple presentations revealed how widely and systematically the White House sought to deliver its list of electoral priorities.

In the course of investigating the U.S. attorney matter and the PowerPoint presentations, Democratic congressional investigators discovered e-mails written by White House personnel using accounts maintained by the Republican National Committee.

For example, they discovered that Jennings, a special assistant to the president and deputy director of political affairs in the White House, was using an e-mail with the domain name of “gwb43.com” that the RNC maintained.

That domain name showed up in e-mail communications from Jennings about how to replace U.S. Atty. H.E. “Bud” Cummins III of Arkansas to make room for Timothy Griffin, a Rove protege, in such a way as to “alleviate pressure/implication that Tim forced Bud out.”

Another Jennings e-mail using the RNC account requested that department officials meet with a former New Mexico campaign advisor who wanted to “discuss the U.S. Atty situation there.”

The growing controversy inspired him to act, Bloch said.

“We are acting with dispatch and trying to deal with this because people are concerned about it ... and it is not a subject that should be left to endless speculation,” he said.

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tom.hamburger@latimes.com