WASHINGTON - From the moment Barack Obama spoke at the Democratic National Convention in Boston in 2004, he has enjoyed a reputation as a politician with a claim to the high ground.

Now, even supporters are questioning whether his administration abused the offices of government for political gain.

"Those who are found to have been responsible for this betrayal of public trust should be fired," Sen. Mark Warner (D., Va.) said of revelations that IRS workers targeted Republican-leaning advocacy groups for extra scrutiny.

On Thursday, the president named Daniel Werfel, a senior White House budget official, to become acting head of the IRS, replacing Steven Miller, who was forced out a day earlier. A second top IRS deputy, Joseph Grant, announced his retirement.

"My main concern is fixing the problem," Obama said at a news conference Thursday. "And we began that process yesterday by asking and accepting the resignation of the acting director there."

The efforts did little to reassure Republicans. House Speaker John A. Boehner suggested the White House had violated the public's trust, and he promised to "stop at nothing" to hold the administration accountable.

"Nothing dissolves the bonds between the people and their government like the arrogance of power here in Washington," he said. "That's what the American people are seeing today from the Obama administration - remarkable arrogance."

Obama said he would not appoint a special counsel to investigate the IRS action because the Justice Department and Congress were already conducting probes.

"We're going to make sure that we identify any structural or management issues to prevent something like this from happening again," he said.

The confluence of the tax agency's actions against small-government tea party groups, the Justice Department seizure of telephone records of reporters and editors of the Associated Press, and the administration responses to the deadly raid last year on a U.S. diplomatic mission in Libya has set in motion a now-familiar Washington cycle of hearings, talk of crisis, and calls for resignations.

Yet it's a terrain that Republicans, particularly in the House, have not shown deftness at maneuvering, and overreach can produce unexpected consequences, including driving support toward the president.

"He's not Richard Nixon," said John Feehery, a Republican consultant and aide to former Speaker Dennis Hastert. "He doesn't look guilty. And I think that's a tremendous advantage."

Columnist Charles Krauthammer, on Fox News, cautioned the party's officials to avoid tossing around talk of impeachment, as Texas Rep. Steve Stockman has done, and to let facts drive public opinion.

"It feeds the narrative of the other side that it's only a political event" by promoting impeachment prematurely, he said. "It is not."

Obama, after several days of criticism, stepped out Wednesday to play offense, releasing internal e-mails regarding the Libya attack response, announcing support for a new law to protect journalists, and accepting Miller's resignation.

"They have to act big and bold to stop the bleeding," Mike Murphy, a California-based GOP consultant, said of Obama and his aides. "This is the first step. Tough, honest, no-spin investigation is the next step."

The president, in confronting second-term errors that may grow to greater proportions, is joining a long roster of predecessors.

Nixon was forced to resign in his second term after the Watergate scandal, which surfaced after burglars with White House ties were caught breaking into the Democratic National Committee's headquarters in Washington. President Ronald Reagan's administration was beset by the Iran-contra affair, in which officials were caught selling arms to Iran in an attempt to free hostages in Lebanon.

President Bill Clinton was impeached after making false statements about his relationship with a White House intern.

In each case, lawmakers in Congress from the opposition party used their perches in committee to keep the story lines in the news.

It's a strategy the current House Republican caucus has tried to implement without much success. Weeks before the 2012 election, the House Committee on Oversight and Government Reform convened to draw attention to the security failures that led to the September attack on the U.S. mission in Benghazi, Libya, that caused the deaths of four Americans.

Less than a month later, Obama won reelection.

But Republicans on Thursday were not sounding hesitant. On the Benghazi e-mails release, Rep. Jason Chaffetz (R., Utah), a member of the House Oversight and Government Reform Committee, said that while he applauded the release of "hand-picked e-mails," the White House should release all the unclassified e-mails.

"I want all the documents released," said Chaffetz, who also made clear that the committee wanted to talk to more officials.

On the IRS, at least three House and Senate committees plan investigations.

Miller, the former acting chief, is to appear before the House Ways and Means Committee on Friday morning. Lawmakers will demand an accounting of what the IRS did and why senior managers failed to act.

"We repeatedly asked what was going on, and they were evasive," said Rep. Charles Boustany (R., La.). "We're going to follow the trail, and we have to start somewhere."

This article contains information from the Associated Press.