He finished the TV taping in the small hideaway office inside the Capitol, threaded his way through the tourists walking out of the Rotunda, seeing heads turn as he went, passed the old Supreme Court quarters, and was stopped by a business lobbyist.

"Just want you to know we're working hard for your bill, senator," the lobbyist said. When the senator replied with a quip, the lobbyist quickly spoke up. "I'm serious. I thought my company would say get out of town and stay out, but they're right in there with you."

He smiled. "They're worried about the deficits and interest rates, aren't they?"

As he started to walk away, a young man stepping forward from the crowd that had gathered asked, "Could I have your autograph, senator?"

He held the piece of paper in his right hand, from which the tip of a fountain pen protruded, said, "I don't write very well," scrawled his name with his left hand, and continued back to the Senate, noticing more heads turn along the way.

Who is this wave-maker, this instantly recognizable figure the fickle populace of Washington treats as the latest emerging political star? Why, and with exquisite irony, the lion of the moment is none other than yesterday's fall guy, Bob Dole of Kansas.

Not so long ago Dole wore the goat horns, historic in cast and heavy in weight. He was tagged with being the architect of Republican defeat. It was his snarling, slashing, unfair, ideological gut-fighter's campaign style as Gerald Ford's running mate in 1976 that caused the GOP to lose the White House.

So it was said, and widely believed.

Now with passage of the big tax increase bill that bears his name, an act that goes against all the election-year instincts of the political animals of Washington and runs against the strongest ideological currents of his own party, Dole fully emerges as a major national leader, and one being praised for his moderation and fairness and bipartisan statesmanship.

He is, the pundits already are saying, a potential president.

Over the past few weeks, at almost any hour from early morning to late night these days, you were certain to catch him being interviewed on television about his role as point man for the president in the tax bill battle that holds political implications far beyond the voting outcome last Thursday. Go to his Senate office and his aides will hand you a sheaf of newspaper articles, columns, and editorials culled from around the country hailing "the New Dole."

Newspapers and writers that in the past had found him unfit for political company are extolling his virtues.

With the paeans from liberal or moderate or mainstream political voices delighted over a tax package that strikes at big business have come a corresponding drumbeat of condemnation from the hard-shell, red-meat conservatives whose darling he once was.

And business, which once looked to Dole as a staunch ally when he was GOP national chairman, now views him with deep suspicion. On the day Congress prepared to vote on the tax bill, for instance, the political consultant Horace W. Busby gave his business clients this assessment of Dole:

"Long a reliable friend of business, he has undergone a transformation this year, keeping business representatives at arm's length, personally and procedurally . . . . The tax bill, principally crafted by Dole alone, is very much in the mode of a Democratic liberal bill, lightly taxing individuals, coming down heavily on investors and business."

These ironies are not lost on Dole. He retains as sharp a wit as his tongue was said to be before, tempered now by a wry sense of introspection.

Dole knows from hard experience that losing teaches the best lesson. And he knows well what it's like to be a loser, first as vice presidential candidate and then, four years later, as one of 1980's many presidential aspirants defeated by Ronald Reagan.

It is typical of the Bob Dole of today that he can take time out from the climactic round of phone calls, meetings, and last-minute lobbying that preceded the crucial House and Senate votes Thursday to reflect on how those defeats have affected, and perhaps changed, him.

"We came so close," he says, recalling the 1976 campaign. "I remember I was talking to President Ford at the time and he said in effect he was going to send me into the briar patch while he stayed in the Rose Garden, which was fine. That was the strategy. I was supposed to go out and take on Carter, which I did. Some say too much. But in any event, we didn't win.

"When you lose and you come that close it's tough. You just sort of set back and reflect awhile on whether you have to change directions or change attitudes or change perceptions. Because we came out of that election viewed by many in the press as the hatchet man, the tough guy. And you don't want that image and you don't know how to change it. So you go through a rehab process, and I think it's gone now. It's hard to get people to focus on things you've done in a constructive way."

Dole was sitting behind his desk in his Senate office Thursday while the tax vote roll call was about to begin, fielding phone calls from Cabinet officers, Senate colleagues, Democrats as well as Republicans, White House lobbyists, requests for press interviews and yet still musing in detached fashion about the new realities -- and responsibilities -- now thrust upon him. Around him were the kinds of mementoes politicians love to display for their visitors, pictures of him with Ike and Ford and three new ones signed "Ron," and a few more personal items. The charcoal sketch, in an inner office, of young 2nd Lt. Robert J. Dole was drawn after machine gun bullets left his right arm permanently paralyzed after a World War II battle in Italy's Po Valley.

"I'm still competitive and maybe combative at times," he said, "and I think the 'New Bob Dole' may be confused with the new responsibility. Not that we were irresponsible before but suddenly you've got to get 11 votes in the Finance Committee and you can't be cutting them off at the knees and asking for their votes at the same time. So you realize it's different."

The theme of responsible political leadership weighs heavily with Dole and the other Republican leaders in the Senate. They have come to power after a generation in the political wilderness and have something to prove. Now, they believe, the results of the tax bill prove it.

"It's a big transformation for all of us to be moved from the minority to the majority," Dole says. "Suddenly we had to produce. We couldn't sit on the back bench and yap and scream and take issue with everything. Suddenly we sat in the driver's seat. And a lot of us, you know, had never driven before. We've gone backwards and we've gone sideways a few times. But we never went forward. I think a lot of people were saying, 'My God, Bob Dole can't follow Russell Long, Howard Baker can't follow Bob Byrd . . . . "

The phone rang. It was Bill Bradley, the Democratic senator from New Jersey. They talked about a meeting scheduled later that day on tuition tax credits. Then Dole switched the subject. "When are you going to help us on the tax bill? You're going to vote for it, aren't you?" he asked.

Pause. Laughter. "Oh, I'm ready," Dole said. "They've got everything in that bill but the kitchen sink." He listened briefly, and spoke again: "Yeah, fine. I think it would be helpful, very honestly, to be crass about it. If someone like yourself would indicate support that might help some of your New Jersey Democrats over there in the House who probably haven't made up their minds yet."

A few minutes later the phone rang again. It was Treasury Secretary Donald T. Regan.

"How we doing?" Dole began. " . . . . Well, you feel very confident. Yeah. Well, I think we're all right over here. There's a potential of 12 or 15 Democrats but we don't want to lose over eight of ours. Well, we're going to lose Hawkins, Kasten, Mattingly, the original three. East is going to vote against you. Goldwater said yesterday he would vote against us. That's five. You've got to allow a little room for a guy like Jesse Helms whose got his neck way out on the excise tax. You've got Harry Byrd and you've got John Warner. That's eight. And there's always a wild card to be played."

To Dole, and the other Republican leaders, last week's tax increase showdown demonstrates, as he says, "that we can do the right thing in Congress, that Democrats and Republicans can get together and can do it. I think there has been a lot of, I won't say mistrust, but lack of confidence among people who make things happen, say in the financial community, that Congress would ever really do anything like this."

It also shows something about Dole, and the evolving relationship of the Republican leaders in Congress with President Reagan.

By their actions, they are all reaffirming the truth of the old adage about politics being the art of the possible. Passion may be more exciting than compromise, and pragmatism may be denounced by the true believers as lacking in principle, but governing requires creating a consensus -- and being willing to admit mistakes and change when necessary.

Dole stands as a perfect example of those facts.

A year ago, as the new chairman of the powerful Senate Finance Committee, Dole helped pass the great Reagan tax cuts. They were the largest in American history. It was, as he says, "easy to give away money to cut taxes."

That entire first year was easy for the new Republican leaders and the new Republican president, obviously, in retrospect, too easy.

"That was sort of heady stuff, to be out front on something like that," Dole says, "but it was mostly the president's victory. We were just hanging on being swept by the Reagan tide. This year it was different. This year has been the year of testing."

Dole now says he and others among the Senate Republican chairmen had doubts about so-called supply-side economics from the beginning. "But we were willing to try it. We wanted to cooperate with the president. That doesn't mean we didn't have our own ideas."

Some time last fall he and others on Capitol Hill began to experience what he calls "a lot of discontent." They began thinking they had gone too far in cutting social programs. They were worried about the growing unfavorable public perception of the Republican Party. It fell to them to begin closing the gap between supply-side theory and reality. As Dole says:

"The perception out there was that we were being unfair, that we were hitting people in the bottom who were helpless and vulnerable, that we were just helping the people at the top. Then the deficits wouldn't go down. In fact, they were soaring. The interest rates wouldn't go down. A lot of us started to say we had to do something. We not only had to cut more spending but maybe raise some revenues.

"We could see as a party we weren't expanding. The president was okay but the Republican Party was not so strong. So we started trying to impress the White House and Don Regan and Dave Stockman and Jim Baker and the president that we had to do more. We couldn't sit back and wait for the millennium to happen."

Out of that came the long effort that culminated in Thursday's House and Senate votes to raise taxes just a year after cutting them.

Neither of those votes had been taken when Dole was speaking, but he was confident of victory and pleased with the way the process had worked.

"I think we've demonstrated that we can provide leadership," he said. "I'm not yet certain we've demonstrated we're sensitive with some of the concerns, but we're working on them."

A pause, and then a smile: "You know, I'm not going to be defensive about my political philosophy. I think I'm as conservative as some of these House Republicans who think we've lost our minds, particularly me."

He laughed, and then reminisced about one more political lesson, painfully learned: that of his 1980 presidential race.

"I learned that you don't get into something with nothing. I had some big theory called the Five Ms: money, management, media, momentum, and I can't remember the fifth one. But I didn't have any of them. I had no money and no management and no media and no momentum. I also learned you can't have a 90 percent attendance record in the Senate and be a candidate for the presidency. You have to say, okay, this is it, or not.

"So I learned not to get into the big league unless you've got a big bat. And I didn't have any bat at all. I was swinging with a toothpick."

That was when Bob Dole was a loser. Now he swings a heavier bat, and drives in winning runs.