By DAVID STOUT
WASHINGTON, Oct. 28 - I. Lewis Libby Jr., Vice President Dick Cheney's chief of staff and one of the most powerful figures in the Bush administration, was formally accused today of lying and obstruction of justice during an inquiry into the unmasking of a covert C.I.A. officer.
A federal grand jury indicted Mr. Libby on one count of obstruction, two counts of perjury and two of making false statements in the course of an investigation that raised questions about the administration's rationale for going to war against Iraq, how it treats critics and political opponents and whether high White House officials shaded the truth.
The charges are felonies and could bring a sentence of up to five years in prison and a hefty fine upon conviction. Perjury is lying under oath, to a jury or other investigative body, while making false statements consists of lying to investigators while not under oath.
Karl Rove, President Bush's senior adviser and deputy chief of staff, was not charged today, but will remain under investigation, people briefed officially about the case said. As a result, they said, the special counsel in the case, Patrick J. Fitzgerald, was likely to extend the term of the federal grand jury beyond its scheduled expiration today.
The indictment constitutes a body blow to the White House, which has faced political problems on several fronts of late and where Mr. Rove and Mr. Libby have been powerful presences - Mr. Rove as the president's alter ego and top political adviser, and Mr. Libby as an important adviser to one of the most powerful vice presidents in American history.
Mr. Libby was widely expected to resign almost immediately. Months ago, President Bush said anyone in his administration who committed a crime in connection with the disclosure of the name of the C.I.A. officer, Valerie Plame Wilson, would not be a part of his administration.
More recently, the White House has retreated somewhat from that position, with Mr. Bush's chief spokesman, Scott McClellan, saying it would not be appropriate to comment in the course of the investigation.
Mr. McClellan said repeatedly at White House news briefings that both Mr. Libby and Mr. Rove had assured him they were not involved in unmasking Ms. Plame. So the charges lodged against Mr. Libby and the ongoing investigation of Mr. Rove offer abundant grist, at least for now, to critics who question the administration's commitment to truth and candor.
As the charges were announced, President Bush was returning to Washington from Norfolk, Va., naval base, where he delivered a speech on terrorism.
If the charges announced today lead to a conviction or guilty plea, the episode will stand in Washington history as another example of a cover-up becoming more serious than the original wrongdoing.
Questions about the extent of Mr. Libby's involvement in the affair intensified this week, when lawyers involved in the case said that Mr. Libby first learned about Ms. Wilson from Vice President Cheney on June 12, 2003, rather than from journalists several weeks after that date. Ms. Wilson's husband, Joseph C. Wilson IV, is a former diplomat who was highly critical of the Bush administration's case for going to war.
As recently as the last few days, F.B.I. agents questioned neighbors of the Wilsons in northwest Washington, seeking to determine whether it was commonly known that she was a C.I.A. officer, a person involved in the case said. Mrs. Wilson sometimes has been known by her maiden name, Valerie Plame.
The indictment of Mr. Libby is the latest chapter in an episode that came to light in the summer of 2003. At first, the matter seemed like a tempest in a political teapot, driven by spite and revolving around the issue of whether anyone had violated an obscure federal statute that makes it illegal, under some circumstances, to unmask an undercover agent.
But well before the charges were announced, the affair had mushroomed into something far more serious. It resulted in the jailing of a New York Times reporter, Judith Miller, who had resisted Mr. Fitzgerald's pressure to testify, and it provided regular grist for administration critics to assert that the Bush White House routinely bullied its political opponents.
On July 6, 2003, Mr. Wilson wrote an Op-Ed article in The New York Times recounting a trip to Niger at the behest of the Central Intelligence Agency that left him highly skeptical of Bush administration assertions about Iraq's quest for nuclear material to make weapons.
Eight days after Mr. Wilson's article appeared, the columnist Robert D. Novak disclosed that Mr. Wilson wife was a C.I.A. operative working on the issue of weapons of mass destruction, and that she had recommended her husband for the trip to Africa in 2002 to look into intelligence reports that Iraq had sought uranium from Niger that could be converted to weapons use. Mr. Novak wrote that he had learned of Mrs. Wilson's identity from two senior administration officials. The columnist has refused to say whether he testified before the grand jury.
The charge against Mr. Libby is not entirely a surprise. Both he and Mr. Rove testified several times before the grand jury about what seemed, at least on the surface, to be a relatively limited sequence of dates and events. Their repeated appearances before the panel stirred conjecture that the prosecutor was checking their testimony for contradictions with the accounts of other witnesses, or indeed to see if Mr. Libby or Mr. Rove had changed their own accounts over time.
News of the indictment came one day after President Bush's Supreme Court choice, Harriet E. Miers, withdrew her nomination after encountering criticism from both the political right and left.
The Bush administration has also been trying for weeks to get past criticism of its initial response to the hurricane-and-flood disaster that struck the Gulf Coast.
Moreover, the charges against Mr. Rove came not long after the indictment of Representative Tom DeLay, Republican of Texas, on campaign fund-raising charges, and amid an inquiry into Senator Bill Frist's sale of stock in a family-owned company. Mr. Frist, Republican of Tennessee, is the Republican majority leader.
Mr. DeLay, who had to step down as House majority leader after his indictment, has called the charges against him the work of a partisan, publicity-happy prosecutor. And Mr. Frist's lawyer has said the senator has done nothing wrong and is cooperating fully in the investigation, still in its early stages.
But the charges against Mr. Libby and the problems, momentary or otherwise, of Mr. DeLay and Mr. Frist have already led Democratic strategists to pronounce as corrupt the Republican stewardship in Washington - meaning the White House and both chambers of Congress - and they will no doubt enter the 2006 and 2008 campaigns portraying Republicans as arrogant and too comfortable with the trappings of power.
It would be a political nightmare for Republicans if the charges against Mr. Libby go unresolved - or have been resolved against them - before the Senate and House elections of 2006.