In an earlier time, when juniors were supposed to live on patience and power only arrived with age, the stern leaders of the House would not have put up long with the likes of Rep. James R. Jones.

A measure of how much the place has changed is that today this unassuming fourth-term Oklahoma Democrat -- still little known to the public at large -- has become a pivotal member of the House, an inside power.

Tulsa's quiet man in Congress pooh-poohs the idea, but he commands an important bloc of moderate-conservative votes in the House. His committees are Ways and Means and Budget; his issues are tax and spend; and the business community loves him.

It has good cause.

A year ago Jones was instrumental in writing and passing a bill cutting taxes on capital gains. It was done as a boon to investment. It also happened to be a boon mainly to the richest part of the population, which does most of the investing.

This year Jones followed on that first success by helping to dilute the "windfall profits" tax on oil companies that passed the House. Now he is one of those pressing for new tax cuts for business in depreciation, and it is mostly Big Business that would benefit, tax analysts say. And he has been promised a vote on an important amendment to limit federal spending, too.

Young Jones inherited his power on Ways and Means when old Joe Waggonner left.

Joe D. Waggonner Jr., a Louisiana Democrat, was for years the swing man on the tax committee, a facilitator who could often forge two minorities -- conservative Democrat and Republican -- into a one- or two-vote majority on issues that counted.

Waggonner's retirement at the end of the last Congress left a void. The 40-year-old Jones quickly moved to fill it. And as often happens on Capitol Hill, where reputation is a form of reality, one success helped produce another. As Robert McIntyre of the Tax Reform Research Group, Jones' frequent but respectful adversary, put it: "Once people think you're a big deal, it builds on itself."

Jones was also helped by a habit of preempting the middle of the road. You can color him moderate; certainly that is how he takes pains to color himself.

Some examples:

In 1978, with the Ways and Means Committee and its chairman, Al Ullman (D-Ore.), stalemated over the Carter administration tax reduction plan, Jones stepped in and hammered out the bill that included his capital gains cut. He carefully called it a compromise.

This year, after the committee approved a fairly strong windfall profits tax on oil, Jones came to the floor and got the House to weaken it. He and co-author W. Henson Moore (R-La.) called that a compromise too.

When Speaker Thomas P. (Tip) O'Neill Jr. (D-Mass.) had some onee else in mind for membership on the Budget Committee, Jones called in his chips and took his case to the Democratic caucus last winter. He won, but he did not call that a compromise. He called it fairness.

But there are no hard feelings, so when the leadership needed votes on a debt-limit bill and a budget resolution, Jones was sought out. He delivered the votes but extracted a promise that a vote would be allowed later on his own proposal to limit federal spending. Democratic leaders aren't keen on his proposal, but he calls it a compromise -- an alternative being a less palatable balanced-budget constitutional amendment.

Jones' successes in committee and on the floor have often caused some discomfiture to the leadership.

"There is a chagrin in the top leadership about Jim's success," commented one of the House's legislative craftsmen. "Most of them are more liberal than Jim. But he succeeds because he fills vacuums. A lot of his success is due to the lack of success of Ullman as a strong leader on Ways and Means. Jim creates a consensus around which he succeeds."

Republicans, at least on the Ways and Means Committee, where they often fall in line with Democrat Jones, play a large role in this politics of consensus and they are loving it.

"One reason we like to work with him is that he consults us," said Rep. Bill Frenzel (R-Minn.). "He's not hidebound. He is very reasonable; he is willing to work through things; he accepts responsibility; he offends no one. You can put his word in the bank. If you have those traits, you don't need very much more t be successful around here."

Outside, in the business community, there is similar unalloyed joy about Jones and his willingness to listen to the lobbyists, work with them and even push them a bit.

Charls E. Walker, a former deputy secretary of the Treasury and now a high-powered business tax lobbyist, scoffs at the theory that he is the brains behind Jim Jones and his tax-breaks-for-business philosophy.

"Jim is a phenomenon. I have never seen anyone like him. He's done it on his own. He's his own man. He is intelligent and politically savvy.There's no flaming rhetoric, he's never out of sorts. He just lays things out." Walker said.

If 1978 campaign contributions are an indication, the business community and its Washington lobbyists positively adore Jones. Political action committees -- most from outside of Oklahoma -- and lobbyists contributed more than 40 percent of his $250,000 warchest.

Notably, Walker's American Council for Capital Formation, which avidly sought and got the capital-gains tax cut that Jones' compromise provided, was one of the most generous.Council members gave him about $14,000, with the bulk of it coming when the compromise bill was being written.

On that, Jones said the other day, "I don't pay that much attention to where the campaign money comes from. I did send a fund-raising letter that I hope is persuasive." The letter talks about his ability to "deliver." t

"When I came here, my colleague Tom Steed [D-Okla.] told me that knowledge is power. So I work hard at it, although I don't think I really command any votes in the House," Jones said. "I just have some ideas about the way the country ought to go."

"On the business side, for whatever reasons, I've been somewhat out front on capital formation. And I've tried to get the business community to be more effective."

That's where Jones has done perhaps his most effective work: in urging business to speak on tax bills with one voice.

"In the past 10 years, each business interest was going in a different direction. So last year I told them that this would be the package and if they agreed, they would have to stay with it," he said.

They did, of course, and the result was the tax bill.

Then Jones talked to other Ways and Means members and Harvard economists on whom he relies about the next step. He settled on legislation to speed up business depreciation rates.

Barber B. Conable Jr. (R-N.Y.), the ranking GOP man on the committee, agreed and hooked up with Jones. "We set out a game plan, tried to get the business community to give up its pet projects and get behind this," Jones said. "I spoke to all of them and told them that divided, they would get nothing. I told them to work up grass-roots support."

A Jones-Conable bill, now with more than two-thirds of the House cosponsoring, was introduced in June. If and when it passes, another phase will be in place.

Next on the agenda, assuming that coalition holds up, will be legislation to reduce corporate tax rates. The idea of all this is to free up more money for capital investment, get the plants humming around the country and put people to work, not to mention beefing up profit. Many reject the idea, but business is giddy over it.

So when Jones announced a few weeks ago that he had decided not to run for a U.S. Senate seat in Oklahoma next year, his friends in the boardrooms were ecstatic. He said he has unfinished business in the House.

It meant that Jones, who has been reelected handily in a historically Republican district, would remain around Ways and Means to keep working that magic.

The magic has worked well at home, too, for Jones has survived several brushes with taint that might have torpedoed any other nascent politician.

He pleaded guilty in 1976 to a charge of failing to report a $1,000 Gulf Oil Corp. contribution to his 1972 campaign. He said he didn't know it was illegal corporate money and paid a $200 fine.

Earlier, he had been embarrassed by the Senate Watergate committee's release of a memo in which Jones told some of his milk-producer law clients that he had convinced President Lyndon B. Johnson to raise milk price supports.

Jones said that was just his own braggadocio, trying to keep a client in the stable, although there was no question about his closeness to Johnson.

In 1965, when he was 25, he became Johnson's appointments secretary and stayed at LBJ's side until he left office in 1969. That he learned well at the knee of a master coalition-builder and filler-of-needs seems clear.

"I learned from Johnson that you need to take a stand, have goals and recognize that you're not infallible. You touch all the bases, find what it takes and you work hard," he said. "At some point, if you touch all your bases and run all your traps, a sensible political solution emerges."

Call it a compromise.