WASHINGTON - Walking through the Capitol last week, Dick Cheney marched past the assembled journalists who hoped to question him, brushing them off in his inflection-less voice with a curt, "Good morning," before slipping behind closed doors.

The vice president had come to buck up House Republicans at a time of growing anxiety about the state of affairs in Iraq, the cost of the reconstruction and the economy at home. And by all accounts, he succeeded. The Republicans left the session noting how "incredibly lucky" President Bush is, as their whip, Rep. Roy Blunt, put it, "to have a partner like the vice president in these challenging days."

The performance was classic Cheney - refusing to engage on the issues with the klieg lights on, but vigorously defending the administration and exerting influence behind the scenes. It highlighted the extraordinary role that Cheney - arguably the most influential vice president ever - plays in shaping nearly every major White House policy.

Yet Cheney's formidable presence has not been an unalloyed asset for the Bush administration. Along with the gravitas, reassuring air and mastery of inside Washington that he has brought has come a measure of controversy that has turned this low-profile vice president into a high-profile target.

Cheney's hard-line posture and recent statements on the Iraq war and its aftermath - suggesting ties between Saddam Hussein and the Sept. 11 attacks as well as other justifications for war that have not panned out - have put the Bush administration on the defensive and Cheney in the spotlight.

Democrats have invoked "Cheney and company" as a sort of shorthand for the hawkish wing of the administration, including Defense Secretary Donald H. Rumsfeld and his deputy, Paul D. Wolfowitz, that made the most forceful arguments for war.

Among Bush administration officials, Cheney painted the most ominous picture before the war, saying that there was "no doubt" Hussein had weapons of mass destruction and that the administration believed the Iraqi dictator had reconstituted his nuclear arms programs.

One of the administration's more spectacular claims - that Iraq tried to buy uranium in Niger - led to a White House retraction. It also spurred the growing scandal involving a former diplomat, Joseph C. Wilson IV, who investigated that claim for the CIA and deemed it spurious. It was Cheney's interest in the implications of an Iraq-Niger connection that led the CIA to look into the matter, Wilson has asserted.

Still, CIA Director George J. Tenet says Cheney was not briefed on Wilson's conclusions. Nor has Cheney been tied to accusations that the White House punished Wilson for his role in forcing the retraction by blowing his wife's cover as a CIA operative.

Alone among top administration officials, Cheney has continued to suggest that Hussein could have had ties to the Sept. 11 terrorists, even though some of the evidence he has offered has been deemed questionable by the CIA and FBI, and Bush himself has said, "We've had no evidence that Saddam Hussein was involved with Sept. 11."

Mary Matalin, Cheney's former counselor who is still an informal adviser, defends Cheney's use of such evidence, saying: "It's not questionable if you have other data that he has that's classified."

At every appearance these days, Cheney defends the decision to wage war in Iraq, saying that Sept. 11, the Bush administration's "defining moment," justified preventive action against a brutal dictator who "gave support to terrorists and pursued weapons of mass destruction."

On the domestic front, Cheney's aggressive effort to keep secret his meetings with oil industry officials while he was developing a national energy policy has turned into a fierce legal battle. The administration plans to appeal to the Supreme Court to avoid a court order to release information related to Cheney's energy task force.

Pointing to Cheney's resistance to releasing the documents, Democrats have complained that the Bush administration is too cozy with big business and operates in private, with little public accountability.

Critics still rail against Cheney's ties to and deferred income from Halliburton, the oil services company he formerly led. The company recently won a no-bid contract worth $1.2 billion to rebuild oil fields and aid the U.S. military in Iraq.

Cheney has said he has no financial interest in Halliburton, though his office acknowledged that he will still earn about $150,000 a year through 2005 in a deal he negotiated while at the company so he would be paid even if Halliburton failed.

Last week, Sen. Frank R. Lautenberg, a New Jersey Democrat, released a report by the nonpartisan Congressional Research Service that concluded that Cheney's deferred compensation from Halliburton amounted to continuing financial interest in the company. Others have asked for investigations into Halliburton's government contracts.

Among Democrats running for president, Halliburton has become a buzzword for their charges of a symbiotic relationship between the Bush administration and corporate America. References to Halliburton have become applause lines in Democratic debates and have even made their way to late-night television.

Remarking on the additional $87 billion the Bush administration has sought from Congress for Iraq and Afghanistan, David Letterman joked: "When you make out that check, remember, there are two L's in Halliburton."