Having worked for six secretaries of State over 20 years, I have a pretty clear sense of what makes a good one -- and with the economic and financial crisis overshadowing foreign policy these days, the selection of an effective secretary of State is now more imperative than ever.

I must confess to a certain bias. In the last 30 years, I believe we've had only two truly consequential secretaries of State. James A. Baker III (whom I worked for and admired) and Henry A. Kissinger (who predated me), with all their imperfections and detractors (and there are many), stand out well above the others. They had different personalities, confronted different circumstances and succeeded and failed in different ways. But they embodied four important qualities that helped them succeed:

The right persona. Freud may have been overly deterministic when he talked about anatomy as destiny, but when it comes to what it takes to be an effective secretary of State, he wasn't far off the mark. The nation's top diplomat needs to be an actor, a teacher, a tactician, an intimidator and a confidant. Most of these qualities are natural and instinctive, rather than learned -- as is the ability to project a strong physical and intellectual presence. When an American secretary of State walks into the room, either here or abroad, his or her interlocutors need to be on the edge of their seats, not comfortably situated in their chairs wondering how best to manipulate the secretary. If anything, they should be worried about being manipulated themselves.

Kissinger and Baker both impressed Arabs and Israelis with their endurance and stamina in negotiations. Both were actors who could yell and threaten to abandon the process (Baker at least twice with Syrian President Hafez Assad and Israeli Prime Minister Yitzhak Shamir; Kissinger at least once with Assad), yet they could also reassure, as Kissinger masterfully did innumerable times with the Israelis and as Baker did with the Palestinians. That mix of keeping their interlocutors off balance but reassured proved indispensable to successful diplomacy. The president's confidence. The assumption that a new president will appoint a secretary of State who is close to him and has his confidence is not always accurate. Of the six secretaries I worked for, only one -- Baker -- had a truly close relationship with his president. And yet this relationship is crucial. You simply cannot expect to do serious diplomacy abroad, or in the sometimes even more perilous world of Washington, without knowing that the president has your back, will not allow domestic interest groups to undermine you or permit his other advisors to do so.

Baker's relationship with President George H.W. Bush was very special -- that of a close friend, even, it sometimes seemed, a younger brother. Kissinger's relationship with Richard Nixon was more distant and competitive, but even so, Nixon recognized Kissinger's talents and gave him room to navigate. Kissinger, particularly during Watergate, used the space provided by the preoccupied president to invoke and use Nixon's authority very effectively.

It takes America's friends and adversaries about five minutes to figure out who really speaks for the White House and who doesn't. If a secretary of State falls into the latter category, he or she will have little chance of doing effective diplomacy on a big issue. More likely, they'll be played like a finely tuned violin or simply taken for granted. A negotiator's mind-set. Teenagers talk on the phone, beavers build dams, and secretaries of State manage crises and solve problems. This means having a smart and tough view of the world, seeing how America's ends and means can fit together, and then knowing how to make them do so. There is little room for ideologues here, or for minds that lack the capacity to reconcile the yes and the no of international relations with all of the myriad contradictions that impose themselves on diplomacy.

The negotiator's mind-set -- the intuitive capacity to see where the deal is, and to put oneself in the middle of the mix to bring it about -- is critical. It's not learned. Baker was a lawyer by training; Kissinger an academic. Both were terrific negotiators who succeeded in negotiations far more than they failed. That Kissinger managed to hammer out three disengagement agreements in 18 months between Israel, Egypt and Syria was truly impressive. Baker's success in getting Shamir, Assad and the Palestinians to the table was a classic demonstration of how to create something substantial out of nothing. Deviousness and toughness. This last point may not be politically correct, but the fact is, effective secretaries of State are manipulators. Deception is sometimes required, and they maneuver constantly, trying to figure out what's necessary to succeed and how to use incentives, pressure, arm twisting and, when necessary, untruthfulness (either by omission or commission) to manage a crisis or close a deal. Baker and Kissinger were not sentimentalists. To close their Middle East deals, they trash-talked Israelis to Arabs, and Arabs to Israelis. They threatened when they had to and conceded when they had to, never losing sight of their objective or of a back door to get out if they couldn't accomplish it. Nice secretaries of State are usually ineffective secretaries of State.

Of course, even an all-star secretary of State cannot guarantee a successful foreign policy. The president's persona, other policy priorities, sheer luck and the uncontrollable and unanticipated flow of events matter more. But an effective secretary who can deal with crises and exploit them as opportunities is critical.

Whether or not president-elect Barack Obama ultimately selects Hillary Clinton or some other talented candidate, it is essential that that person possess many of the qualities that made Kissinger and Baker so successful and that America now needs in its 67th secretary of State.