In politics no less than war the greatest tribute a commander can receive is praise from the leader of the opposing troops.

Consider then the case of Thomas P. (Tip) O'Neill Jr. and Ronald Wilson Reagan, two old pols from competing parties who hold sharply differing views on the political process and proper direction of the country. To hear O'Neill the Democratic speaker tell it, Reagan the Republican president has proven to be "one hell of a pol. He's a master."

"I think he's going to remain popular, to be perfectly truthful with you," said O'Neill, who as leader of the House Democrats has suffered defeat after defeat at Reagan's hands.

"People like him as an individual, and he handles the media better than anybody since Franklin Roosevelt, even including Jack Kennedy. There's just something about the guy that people like. They want him to be a success. They're rooting for him, and of course they're rooting for him because we haven't had any presidential successes for years--Kennedy killed, Johnson with Vietnam, Nixon with Watergate, Ford, Carter and all the rest."

Now, O'Neill says, he's determined to follow the advice he received months ago: "Tip, an awful lot of guys underestimate this guy. Don't you make that mistake."

Democrats like O'Neill, who once wondered whether the new president would be up to playing in the big leagues of Washington, are not the only ones who are reevaluating the abilities of the 40th president of the United States. Republicans are reassessing him, too.

Reagan, as a Republican admirer in Congress observes, is a "high-risk president." Today, a year after his great electoral landslide victory, the risks he faces grow greater. His presidency stands at a critical juncture. The outcome of his economic program remains highly in doubt, with a recession acknowledged, his plans to balance the budget by 1984 abandoned, unemployment rising, and pressures on the financial markets increasing.

The direction of his foreign policy continues uncertain. The differences among his key advisers are spilling out into poisonous public disputes. The ability to carry Republicans to victory and possible political majority status through his vaunted popularity becomes less sure after last week's election returns. And although there has been a notable positive shift in perception about Reagan's political skills since the election, new questions are being asked about his leadership on both sides of the political party aisle in Washington.

Paradoxically, in view of his signal success during his eight months in office, his presidential performance to date has allayed many of the early doubts about him, and raised new ones.

For instance, as the country drifts into recession, will Reagan's personal charm dissolve into frustration? Does his style of command give him enough control over the direction of the government? How will he react if he begins to experience defeats in Congress, amid signs that his economic program is not working?

As he grapples with a host of problems that likely will determine the success or failure of his administration, Republicans and Democrats alike find themselves taking another hard look at Ronald Reagan.

The politicians and press of Washington have been in this position before. They've misread and misjudged Reagan in the past. It's possible the Reagan story a year from now will show them to have been wrong again.

But if they have erred, they also have gained insight into the character of this president. In their process of constant Reagan-watching they have cast aside earlier impressions.

Just after the election last November, a group of Republicans, members of Congress all, met with Richard M. Nixon at a private dinner. They asked him what kind of president he thought Reagan would be.

Nixon was complimentary, extolling Reagan's virtues, praising his personal traits and political beliefs. Finally, one of the Republicans spoke up.

"Mr. President," he said, addressing Nixon, "you've given us all the positives, but what are the negatives?"

Nixon replied:

"He may be too nice to be president."

A year later that view of Reagan, the nice guy, remains unchanged. The view of Reagan, the politician, has undergone a major revision.

No longer are there questions about his being too nice to do the job. Even Republicans now say privately that Reagan practices the toughest brand of political hardball Washington has seen in years. They wonder whether the genial Reagan demeanor doesn't mask many of the qualities of Machiavelli's political fox. And political opponents know that, personal charm notwithstanding, Reagan has a stubborn streak that makes him a formidable foe.

His aides speak of the "tough colonel" in him.

After watching Reagan perform, leading politicians in both parties agree on other aspects of his presidency. They say he has demonstrated two essential ingredients of political leadership missing from his immediate presidential predecessors.

He has shown how powerfully the politics of personality can affect American life, and how effectively the politics of consistency can work in Washington.

Today, as policy shifts are being forced by events, doubts about Reagan's consistency in both foreign and domestic affairs are being heard. How well the politics of personality will work in what looks to be a period of adversity ahead remains to be seen.

But, curiously, the central questions about his presidency today remain much as they were a year ago. They are personal.

Risks, again. The politician who raises that issue has been a close observer of the Reagan presidency and holds a major Capitol Hill position. He says of the president:

"He's on a high-risk course. He wants to change things and wants to make the changes as irreversible as possible so that it will be difficult, if not impossible, to undo them. He not only cuts taxes, but he indexes them so they'll stay cut. He not only cuts government programs, but he makes block grants to the states so they'll be more permanent. He not only cuts out federal employes, he cuts out entire departments.

"Real change is the hardest thing to bring about in Washington. Washington resists it. But change is always fraught with risk, and Reagan is fraught with risk. Foreign policy can go terribly sour. Foreign policy probably can't help you, but it can hurt the hell out of you. The economy can go sour. That's the whole central issue and there are a lot of variables he cannot control and that may not work. A lot of things can go wrong for Reagan, terribly wrong."

Perhaps the biggest change at this point in the Reagan presidency involves attitudes about Reagan. Politician after politician interviewed for this article, most of them Republicans, expressed surprise about how their views of the president have altered.

"The worry about Ronald Reagan when he came here, to judge from everything written and said about him, was whether he could last longer than 9 to 5 without his cue cards," says a prominent GOP senator. "Well, he's certainly demolished that image."

He has demolished more than that.

Despite his long public career--eight years as governor of the nation's largest state, California, and national exposure as a presidential candidate--political Washington still was uncertain about him.

The fear about him, widely held, was that he was a hollow man, poorly informed, who approached the problems of governance casually and was content to let others run the office. They would make the great decisions of state, while he would perform as a largely ceremonial figurehead. His would be a laid-back presidency in a time signaling a national return to laissez-faire.

Thus, the brief against him. It has proven to be wrong in almost every respect.

A different portrait of Reagan emerges from conversations with those who have been dealing with him. Its central dimensions take this form:

He is a self-assured, confident man who functions without any need to prove himself to anyone at any time. In that sense, he lacks the arrogance, or insecurities, of some presidents. The presidency doesn't awe him; he's not uptight in the job. Those who have known him for years say he has changed hardly at all since entering the White House.

He has a consistent, coherent and conservative political philosophy, one shaped over many years and to which he strongly, indeed stubbornly, adheres. While others may question whether he's in control, there's no doubt Reagan is the man in charge and that he is determined to stay the course on what he believes.

He has the ability to make decisions cleanly without brooding and then not worry about them. "He never loses sleep," says a White House official who came with him from California.

He can take bad news in stride, and adapt to it quickly. When the Republican congressional leaders, Sen. Howard H. Baker Jr. of Tennessee and Rep. Robert H. Michel of Illinois, told him directly that his plan to revamp Social Security wouldn't fly politically, Reagan didn't like it.

He swung around in his chair, and showed them a speech draft on a yellow pad he was preparing on that subject. But he listened, accepted their arguments and dropped his plans. He is said to have been similarly flexible on his economic program, never having been wedded to the three-year tax cut idea in advance, and taking a far more pragmatic view than is generally realized.

He has his dogmatic side, however. Some believe he is, to a degree unusual among leading public figures, locked into a mindset emanating out of the America of World War II.

In a city of president watchers, where the remnants of past administrations and many of their leading players remain in place like political geological layers, the president with whom Reagan is most often compared is Dwight D. Eisenhower.

But invariably, when that analogy surfaces within hearing of an Eisenhower administration member, a caveat is entered. "He isn't up to smoke as Ike was," is the way one person put it, meaning Reagan is not as savvy or smart as Eisenhower.

Among the group closest to him, Reagan is depicted as being extremely well read and informed. That is not the general impression outside the Oval Office atmosphere. "He doesn't read heavy books and he doesn't use long words," says an influential GOP member of Congress, "but he doesn't have to."

Others judge him to be less well informed on the intricacies of issues than most recent occupants of the White House, and say he is not comfortable in discussing details. He prefers broad generalizations and leaves specifics to others.

Not surprisingly, most observations about Reagan involve his personality. But there, too, there are surprises.

Washington continues to abound with anecdotes about his genial nature:

A senator recalls seeing the president's eyes mist over during an Oval Office conversation in which the hardship problems of a constituent were recited. A congressman tells of the president calling to cheer up an ill member of his family. A Republican describes Reagan drawing aside Barbara Bush, the vice president's wife, to ask, with concern, "Tell me, Barbara, is George really happy."

What is not understood are signs of his stubbornness and glimpses of temper.

People will describe how he gripped his chair tightly as if to control his anger when a GOP senator wasn't buying his argument during an arm-twisting session before the AWACS vote; how the sparks flew during another meeting when he complained that Republicans were not showing proper party loyalty in supporting him; how disturbed he gets when information leaks to the press or when accounts of internal administration discord surface publicly.

"You guys have got to watch your staffs," he is said to have ordered.

Before the recent eruption involving Secretary of State Alexander M. Haig Jr. became front page news, sources say Reagan responded to complaints about the bitter turf war between competing economic advisers in the Treasury Department, budget office, and Council of Economic Advisers by threatening to fire anyone who speaks out against the administration's stated positions. The White House denies that, but there's no doubt of the president's concern about maintaining a unified public front, a commodity lately in short supply.

And in more personal ways people say that, no matter how much they see him, they really do not understand Reagan. The common portrait of Reagan is of a very anecdotal, very charming, very pleasant--and very aloof--politician.

It is Reagan's political style, though, that makes the greatest impression. Tip O'Neill again:

"He's always got a disarming story. 'Tip, let me tell you the latest story.' I don't know where he gets them but he's always got them, stories about the World Series, football games, everything. 'Tip, you and I are political enemies only until 6 o'clock. It's 4 o'clock now. Can we pretend it's 6 o'clock?'

"You know, I said to him one day that 97 percent of the economists that I talk to (they'd love to talk to you but can't get through) think your program's not going to work. And he laughs and says, 'Well, I guess it's the 3 percent that I talk to that have been right all along.' How can you dislike a guy like that?"

This is not the season for disliking Ronald Reagan. Whether the harsh realities of Washington politics and the cruel policy choices that he surely will be forced to make will change the positive feelings about him in the months ahead remain unknown.

Already Reagan shows increasing signs of frustration as he encounters the problems of the presidency. Like other presidents, he'd like to have more authority to carry out what he believes to be his mandate. He tells a group of editors he wishes he had line veto authority over legislation as he had in California.

And he displays uncharacteristic asperity in public. His eyes were flashing the other day when he snapped out a response to reports that a top-level shuffle of his administration was about to take place. People who wrote that were "blowing smoke," the president said, in obvious anger.

These provide fresh clues for this capital of self-taught Reagan students. Again, new wisdom and new questions are forming about him.

To some Democratic opponents like O'Neill, Reagan's political approach poses this paradox: "He's cutting the heart of the American dream to own a home and have a good job and still he's popular." To some Republican supporters, who desperately want him to succeed, there are other concerns.

"In some ways I'm more puzzled than I was a year ago about Ronald Reagan," one of them says. "I see the charmer but I also see something else. I see us as being in every bit as much trouble as Wall Street thinks we are. The deficits are going to be massive. The interest rates long-term could be terrible. There are a lot of scary economic conditions building up. And I wonder: Does the nice guy see the same things I see?"