Railroaders place to shoot the shit.

Stephen Crowley/The New York Times

Updated: April 29, 2009

Observers of the George W. Bush's administration may argue about just how much power Dick Cheney had within it, whether his standing went up or down, whether the reality exceeded or fell short of conventional wisdom. But virtually all would agree that Mr. Cheney was the most powerful vice president in American history.

No other vice president ever in essence picked himself for the position, as Mr. Cheney did as the head of Mr. Bush's vice-presidential search in the 2000 campaign. And none ever arrived at the White House as the most experienced member of the presidential team. In January 2001, Mr. Cheney's only rival in knowledge of Washington's ways was his closest ally in the Bush cabinet, Defense Secretary Donald H. Rumsfeld.

In the administration's early days, Mr. Cheney was put in charge of developing energy policy, one of Mr. Bush's top priorities. But his real preeminence was established after the Sept. 11 attacks. On that day, it was Mr. Cheney who took charge at the White House and directed the first response.

After the attacks, Mr. Cheney became the leading force in closed-door discussions for a sweeping and aggressive response. In public, he became the strongest administration spokesman for the invasion of Iraq, arguing in a speech in August 2002 that Saddam Hussein would "fairly soon'' have nuclear weapons. He also spoke of the possibility of a connection between Mr. Hussein and Sept. 11th, even after both the C.I.A. and Mr. Bush had discounted such reports.

During Mr. Bush's second term, the president was said to have moved away from Mr. Cheney's point of view on a number of foreign policy questions, siding with Secretary of State Condoleezza Rice on issues like the resumption of negotiations over North Korea's nuclear policy.

After Mr. Cheney left office, several former officials said that in the final days of the administration, he argued strongly and unsuccessfully with Mr. Bush to pardon his onetime chief of staff, I. Lewis Libby Jr., leaving him at odds with Mr. Bush on a matter of personal loyalty as the two moved on to private life.

Mr. Libby was convicted of four felony counts in March 2007 for obstruction, perjury and lying to investigators looking into the leak of Valerie Wilsons employment with the Central Intelligence Agency. Mr. Bush commuted Mr. Libbys sentence, wiping out the 30-month prison term imposed by a judge. He let stand the conviction and lesser penalties, which meant that Mr. Libby, a once-influential lawyer, could no longer practice.

Mr. Cheney's approach to his post-vice presidency has been as unconventional as his time in the job. He  has upended the old Washington script for former presidents and vice presidents, using a series of interviews -- the first just two weeks after leaving office -- to kick off one last campaign, not for elective office, but on behalf of his own legacy. In the process, he has become a vocal leader of the opposition to President Obama, rallying conservatives as they search for leadership and heartening Democrats who see him as the ideal political foil.

At a time when his party has no high-profile leaders on Capitol Hill, Mr. Cheney is in effect the ranking Republican speaking out against Mr. Obama. His message has been amplified -- on television, in op-ed pieces and elsewhere -- by an informal band of supporters.

In his interviews, Mr. Cheney has hit back at Mr. Obama's repeated repudiation of the Bush administration. Speaking to Politico in February, he warned of a "high probability" of another terrorist attack. On CNN, he suggested that Mr. Obama was using the economic crisis to justify a big expansion of government. On Fox, he agreed when Sean Hannity asked if Mr. Obama was "telegraphing weakness."

Mr. Cheney had appeared on Mr. Hannity's show to respond to Mr. Obama's release of Justice Department memos outlining guidelines for brutal interrogations of terrorism suspects to demand that the administration declassify other memos that he said would show the intelligence such techniques had produced.