One is an old warrior, the other a young renegade.

The older man measures his politics against Lyndon Johnson, with whom he once served, the younger against Ronald Reagan, whom he has been recently serving. But Texas Reps. Jack Brooks and Phil Gramm have found something in common this spring--a host of challengers in the Democratic primary.

Brooks of Beaumont is running against four conservatives in the 9th Congressional District along the Gulf coast who say he is too liberal, too old and too out of touch to be in Ronald Reagan's Congress. Gramm from College Station faces among his three challengers in the 6th District south of Dallas the son of the man he succeeded, the late Olin (Tiger) Teague, who blames Gramm for the sins of Reaganomics and the revolt of the Boll Weevils.

Both Brooks, 59, and Gramm, 39, believe it is possible to win an outright victory on May 1 and thus avoid an embarrassing runoff. But neither is leaving it to chance. They are running costly, well organized campaigns to blunt their challenges, and each has spent considerable time at home recently protecting his seat.

Of the two, Gramm appears to be in the stronger position. Perhaps because he believes he can win a big victory, he is encouraging the idea that the voting will be a referendum both on the president's economic policies he helped shape and on the fact that he turned his back on fellow Democrats to aid the Republicans.

The scrappy Brooks hopes to avoid a runoff simply because he wants the pleasure of defeating four opponents he casually refers to as "dogs" and "little men."

The challenges to Brooks and Gramm are the two most significant congressional primary races here this spring, but hardly the only entertainment. All together, there are contested primaries in 15 of the 27 congressional districts.

Redistricting is one reason. It added three new districts to the Texas delegation, and by the time the issue bounced from the legislature to the federal courts to the Supreme Court, it was April before new lines were firmly set.

All this confusion set off a game of musical houses in the Dallas area among a flock of candidates seeking the most hospitable district and trying to figure out whether they lived in it.

In addition, three incumbents retired and there is an unusual number of challenges to incumbents.

John Olin Teague, 42, is a slim former Air Force fighter pilot whose father represented the 6th District for 32 years.

"I am my father's son," Teague says. "I'm not running on my father's coattails, but Dad was a very capable and honest congressman. If I can do 70 percent of the job he did, I'd be the second best congressman the district ever had."

If his name were Smith or Jones, there is little doubt that Jack Teague would be quietly selling real estate in Bryan.

But disgruntled Democrats who would like to punish Gramm for his leadership role in helping Reagan last year--he cosponsored the president's budget and lobbied for the tax cuts--persuaded Teague he was the only person in the district who might be able to administer the whipping.

Teague says he needed little persuading. Having just digested Office of Management and Budget Director David A. Stockman's confessions in the Atlantic Monthly, he says he was sick to his stomach.

"I was appalled at what I read," he adds, and he links Stockman "and his spy Gramm" in his attacks on Reaganomics. "I think people are beginning to realize that Reaganomics is Hooverism."

Teague has made Gramm's defection to the Republicans a central part of his campaign.

"Phil Gramm has chosen to castigate the Democratic Party, but he has chosen to run as a Democrat because it's the expedient thing to do," he says. "If he ran as a Republican, he wouldn't be elected."

Teague's slender candidacy has become a lightning rod for national Democrats who have so far failed effectively to chastise Gramm. Party officials in Washington talk gleefully about Gramm's possible demise.

But Gramm is unrepentant.

"The independence issue is a phony issue," he says. "To be a spy, you have to have a secret identity. I failed on that score." He says the party issue has been raised as a diversion by critics of his policies who know the president and the administration program are popular in the 6th District.

Indeed, not even Teague will attack Reagan. He says he shares the president's goals of reducing the size of the federal government through tax and spending cuts, although he suggests that Stockman and Gramm misled the president on the his economic package.

And Teague has problems, one of which is spelled m-o-n-e-y. He once talked of spending $200,000 for his campaign. Now, with fund-raising lagging behind expectations, he says he will spend $65,000 to $75,000.

"We're not destitute, but we have to watch our pennies," he says. A Washington fund-raiser organized by former Democratic National Committee Chairman John C. White and former Texas representative Bob Eckhardt drew only about 50 people in March.

"I raised at least five times as much as he did from that fund-raiser," Gramm boasts, claiming that the attention Teague got sparked his supporters to ante up.

Teague has only a small campaign staff, little money for advertising, and is not a dynamic campaigner. Even his principal asset, his name, is of only limited value in a district that has changed considerably since his father's prime years.

Two other candidates are given little chance of running close to Gramm, although the crowded field could help produce a runoff.

Gramm, in contrast, began the year with more than $400,000 in the bank and has been nothing if not ecumenical in seeking political aid. He sought the recommendation of White House political adviser Lee Atwater for help in hiring someone to run his phone banks and took the advice of liberal Democratic Reps. Thomas J. Downey (N.J.) and Les Aspin (Wis.) for a pollster.

And if party leaders had hoped that the Teague challenge would chasten Gramm, they should hear his message on the campaign trail. "I hope you will send me back to Washington to finish the job you asked me to start," he says.

In the industrial triangle of southeast Texas, Brooks is fighting a different battle. The dean of the Texas delegation, chairman of the House Government Operations Committee, Brooks has drawn a powerful challenge from the right.

Three young conservatives, who sound as if they would be happier in the Republican Party, are running for the Democratic nomination, and there is only one issue in the campaign: the incumbent.

Two years ago, Brooks avoided the embarrassment of a runoff by 277 votes when a young bus station manager named W.L. (Bubba) Pate challenged him.

Brooks learned his lesson. He opened two full-time district offices, made frequent trips back home and laid the groundwork for the first full-scale modern campaign in his career. He also hired the man who helped House Majority Leader James C. Wright Jr. of Fort Worth fend off a conservative Republican challenge in 1980.

But Brooks' 1980 race persuaded others that he remained vulnerable. Besides Pate, the field includes Tom Combs, mayor pro tem of Beaumont and great nephew of the man Brooks succeeded in Congress; E. Douglas McLeod, a former state representative from Galveston, and a fourth candidate who is well behind.

Last week, Brooks met his challengers in a televised debate, something he has avoided in the past, and they cut him several good nicks.

They attacked his vote in favor of sizable tax deductions for members of Congress, blamed him for the nation's economic ills by linking him to Democratic spending habits, charged him with being an absentee landlord to his district and bluntly called him too out of touch to serve effectively.

"We need to send somebody to Congress who knows how it is, not how it was," said Pate.

Unlike Gramm, Brooks recanted on some of his earlier beliefs. "Busing has seen its better days," he said at one point. Later he proudly told the audience he had opposed the foreign aid bill last year. At another moment, he invoked Lyndon Johnson as a champion of the balanced budget.

Armed with two black briefing books, he attempted to smother his opponents with his knowledge of Washington. "I have built up a tremendous reservoir of seniority and influence," Brooks said of his 30 years in Congress. "It belongs to the people of the southeast Texas coast."

Despite the rhetorical wounds he has suffered, Brooks appears reasonably healthy politically. Polls show him as the clear front-runner, with Pate and Combs scrambling for second place.

Although many people believe there will be a runoff, Brooks might be able to avoid one if his campaign can get his supporters to turn out in greater than normal numbers.