Because the role of the vice president is vaguely defined in the U.S. Constitution, each office holder -- especially in recent administrations -- has carved out his own job and wielded influence to the extent allowed by the president. In the case of Vice President Dick Cheney, he was a key architect of the war on terror and the Iraq War, and he has played a significant role in shaping domestic policy. Cheney's influence has been so great that many scholars consider him the most powerful vice president in modern American history.

As President Bush's vice president, Dick Cheney has brought a wealth of experience to the job. A former White House chief of staff under President Gerald Ford, a former congressman from the western state of Wyoming, and defense secretary under the first President Bush -- Cheney knows how Washington works.

And this may be why when Mr. Bush ran for president in 2000, he chose Cheney to be his running mate. "Dick Cheney is a good man who is well-liked and respected by his colleagues. I'm proud to call him my friend," Mr. Bush said at a time. 

Cheney as a Vice Presidential Candidate

Stephen Hess, an expert on the presidency at the Brookings Institution in Washington, says there were various factors that made Cheney an ideal vice president for Mr. Bush. "It was clear from the beginning that Dick Cheney was not going to run to succeed the president. So their interests never separated, as they often do. In the Clinton-Gore team, after awhile, it was clear Gore had very special interests as vice president in wanting to be a president. That didn't happen here," says Hess. "Secondly, George W. Bush, who had no national experience, his experience was entirely as a governor of a state, chose Dick Cheney very specifically because of his very deep national experience. So he chose him because he knew how to run things in Washington."

The U.S. Constitution assigns no specific role for the vice president, except to preside over the Senate and cast a vote when there is a tie. Vice presidents, however, do provide for instant succession in the event a president dies or otherwise leaves office before the end of his term.

Past vice presidents have tended to travel a lot, representing the president overseas. And despite having no formal authority, some have carved out specific areas of interest to work on for the president, such as Al Gore who spearheaded President Bill Clinton's environmental policies.

Redefining the Office

But Cheney, the nation's 46th vice president, seems to have been especially influential, and apparently heavily involved in major foreign and domestic policy decisions -- from the war on terror to energy policy.

Norman Ornstein, a political expert at the American Enterprise Institute here in Washington, says, "There are a couple of things that emerge about Dick Cheney. The first is that he is an extraordinarily savvy and tough-minded bureaucratic infighter. He knows through decades of experience how the buttons are pushed, how to make things happen and how to keep things from happening. What we've got is somebody with experience and savvy who has strong views, who has decided to assert those views across the widest range of areas."

These areas include the Iraq war, the interrogation and treatment of terrorist suspects, and picking potential nominees to the Supreme Court. His impact on each of those policy areas was described in a recent series of articles in The Washington Post newspaper. In one case involving domestic policy, The Post described how Cheney intervened to reverse a government ruling on water use in the western state of Oregon. The reversal allowed for more irrigation to benefit drought-stricken farmers, but also led to the deaths of tens of thousands of salmon -- an event that had been predicted by government biologists.

Exact details of the working and personal relationship between President Bush and his vice president are not publicly known. But when asked recently to comment on the subject, White House spokeswoman Dana Perino put it this way: "I think that the president thinks of the vice president as a very close and trusted advisor -- somebody who has nothing but the country's best interests at heart."

A Mixed Assessment

But a widely-publicized attempt by Cheney earlier this year to ignore an executive order on handling classified information has generated criticism of the vice president. His reputation also suffered following the conviction of his top aide, Lewis "Scooter" Libby on perjury charges in a CIA leak case, in which the identity of an undercover officer was revealed to the press.

Again, political scientist Norman Ornstein: "Having a vice president in the loop, having a vice president act as a trusted confidante of the president, as a strong political adviser, even as somebody with a delegated, substantive role, is a perfectly good and appropriate thing. Having a vice president who has kind of a free rein to roam over the landscape, often very careful not to leave his fingerprints on things, and who has such an expansive view of his own power and imperviousness to checks and balances, is pretty alarming frankly."

But as long as he retains the trust of the president, Dick Cheney seems likely to continue to work the levers of power in Washington.

This story was first broadcast on the English news program, VOA News Now. For other Focus reports click here.