He was advance-billed as the first President Pro Tem of the whole Congress, an imperial force who would use a combination of wits, experience and gravitas to move the Bush administration’s agenda through pliant Republican majorities in both chambers.

Things haven’t quite turned out that way. After two full years, during which time the Senate has changed hands twice and nearly all attention has shifted to the war on terror, Vice President Cheney has emerged with an uncertain role on Capitol Hill — every bit the powerhouse, but hardly imperial in wielding his influence.

More than a few Republican aides say Cheney is especially known to “parachute in” — a term of art in legislative craftsmanship, most often used to describe senior Members who enter debates after the heavy lifting has been completed.

With Cheney, however, the expression is used to suggest he is more like a “fixer” these days for the White House. “It’s especially true with the conservatives and on defense issues,” one senior GOP aide said. “If Cheney says it’s good, it knocks down a lot of the barriers.”

Conservatives who had spent much of the 1990s complaining about AmeriCorps, the volunteerism program that was a pet project of the Clinton administration, had been leery of Bush White House plans to preserve it, while making changes. That is, until Cheney entered the picture.

“It allayed people’s fears, because he was stepping out on it,” a GOP aide said. “They don’t use him gratuitously [at the White House]. They use him sparingly, which gives it more weight.”

In spite of security measures since the Sept. 11, 2001, terrorist attacks that have often consigned Cheney to an “undisclosed location,” Members say the vice president attends virtually every Republican leadership meeting at the White House, and he has been known to regularly attend the Senate GOP’s Tuesday policy luncheon. Lawmakers say his role is mostly passive on these occasions, listening to the concerns expressed by the lawmakers rather than pressing the administration position.

“He deals with Members as if he was a Member, as he always has been here,” House Majority Whip Roy Blunt (Mo.) said. “I mean, it’s total collegiality.”

Blunt was alluding to the decade Cheney spent in the House — the last two weeks as Minority Whip — before he was drafted as Defense secretary under the first President George Bush.

Members and administration officials suggest that experience has imbued Cheney with an “institutional” view of Congress and its prerogatives that has been critical in discussions between the branches.

It would seem an unusual designation for the administration official whose resistance to demands for information from the General Accounting Office led the Congressional agency to file suit. (The GAO recently dropped the suit, citing concerns about time and cost.) In fact, Cheney was a firm backer of executive privilege even as a Member of Congress.

But GOP Members and aides often cite Cheney as perhaps the only senior administration official to show a consistent inclination to defer to Congressional decision-makers on matters of legislative development and strategy.

One senior aide to Speaker Dennis Hastert (R-Ill.) recalled a critical moment in 2001, when GOP leaders “sent up flares” that they were hoping to carve up the White House’s 10-year, $1.3 trillion tax cut and move it through the House as separate pieces. The stratagem was not well-received at the other end of Pennsylvania Avenue, until Cheney came in.

“He was the first person to really listen” to the House leadership, the Hastert aide said. “He has an innate feel for these things in a way that others don’t.”

It was Cheney, Congressional insiders say, who personally broke a serious deadlock last year on a $10 billion supplemental appropriations measure that the White House had sought as a “war reserve.”

The administration had pushed Congress to steer the entire allotment into a rainy-day fund at the Pentagon — an approach that irked appropriators, who saw this demand as an encroachment on their role in the process. Cheney stepped in and brokered a compromise with the spending committees that divided the money between the CIA and the Pentagon.

“This has been a pattern,” one senior appropriations aide said, citing recurring personal interventions by Cheney in the spending process. Such forays have been necessitated, in part, by the near-complete collapse in dialogue between appropriators and the White House’s Office of Management and Budget. “You can actually have a dialogue with him. With OMB, it’s a monologue. [Cheney] at least understands we have a role here.”

Members say the vice president is almost always at the center of discussions on national security and defense matters, as well as energy issues. He was the principal link between the White House and the Intelligence committees in the aftermath of the Sept. 11 terrorist attacks, when lawmakers began searching for answers.

Rep. Rob Portman (R-Ohio), a Cheney confidant who serves as a liaison of sorts between the House GOP leadership and the White House, suggested Cheney’s bailiwick has been national defense, but his domain extends to the “toughest issues.”

“[Former Vice President] Dan Quayle did a lot of great things, but he never did as much up here as Cheney does,” said Portman, who served in the first President Bush’s legislative affairs shop. “[Cheney] is such a complete surrogate.”

Indeed, as appropriators recently insisted that OMB Director Mitch Daniels be cut out of the final rounds of negotiations on a consolidated spending measure for fiscal 2003, it was Cheney who stepped in to hammer out the final draft, going through many portions of the bill line by line with lawmakers, according to sources on the Appropriations committees.

It was one reason that GOP leaders and appropriators were furious last week when President Bush criticized Congress for its failure to fully fund so-called “first responders” in that very same omnibus appropriations bill.

“They kind of acted like they were surprised to see how things turned out — which is absurd,” one top GOP leadership aide said last week. The fact is, Congressional insiders said, the vice president was sitting at the table, working out the details.

Cheney’s office acknowledges the vice president’s role in painting the “big picture” with appropriators, but insists that he was not involved in “line-by-lines” on the omnibus and was not aware that appropriators had tinkered with the homeland security spending.

The episode has introduced a new degree of wariness to relations between the White House and the Congressional GOP. But there has never been any question that Cheney’s first allegiance is to Bush and his political and policy interests.

This could be seen perhaps most vividly during the Senate GOP leadership crisis that preceded the 108th Congress, when Sen. Trent Lott (R-Miss.) faced a storm of criticism over remarks suggesting that the country would have been “better off” if former Sen. Strom Thurmond (R-S.C.) had been elected president on a segregationist ticket in 1948.

As the controversy raged, Lott aides leaked to the press that Cheney had called his friend and former Congressional colleague before a critical appearance on Black Entertainment Television to “wish him luck” — a signal of support that appeared to be at odds with Bush’s strong public condemnation of Lott’s original remarks.

But when reporters phoned the vice president’s office for confirmation, Cheney aides denied the call had been made, further isolating Lott as he struggled to survive. From there, it was a only a matter of days before Lott was forced to abdicate his role as party leader.