One of the petroleum industry's best friends in the House is ready to challenge one of its best friends in the Senate, and the battle for campaign dollars may turn as fierce as the struggle for votes.

The challenger is Rep. Bob Krueger (D-Tex.), a Shakespearean scholar turned energy expert.

He wants the seat held by Sen. John Tower, chairman of the Republican Policy Committee.

After spending most of the past week quarter-backing a powerful drive for gas deregulation in the House Commerce Committee, Krueger will spend the weekend in Texas.

On Monday he plans to greet supporters at a Fourth of July rally across the street from his home in New Braunfels, and reveal his "future political plans."

No one doubts that they include an announcement for the Senate.

Not only has he mailed out 30,000 invitations promising nickel beer and free watermelon, but he has also taped a five-minute announcement that will blanket Texas television stations Monday morning.

In a state where contributions from oilmen can be of crucial political importance, the possible division of the industry by a Krueger-Tower battle is raising special interest.

Krueger is a tall, elegant bachelor with a reputation for a razor-sharp mind and an overwhelming confidence in his own destiny.

Born in the thriving German-American town of New Braunfels 41 years ago, he spent most of his adult years far from his west Texas base, earning a doctorate at Oxford and serving as a professor and dean at Duke University.

He returned home just in time to win the 1974 primary and general election in a congressional district that boasts 10 times as many sheep and goats as people.

In emerging as a persuasive grass-roots campaigner who could win both liberal and conservative votes, Krueger spent $374,000 tops for any House candidate that year.

If he wins the Democratic nomination next year, Krueger will come up against another formidable fundraiser in Tower.

In his 1972 reelection victory, Tower spent $2.5 million, a record at the time.

Interest in early fund-raising by Krueger and Tower has centered on oil because of the roles played by both men in natural gas deregulation efforts.

At the recent convention of the Texas Independent Producers and Royalty Owners Association in San Antonio, they were featured in back-to-back reports on legislation.

It would be hard to choose the winner of this not-so-subtle competition. Both men earned standing ovations, but the mere fact that newcomer Krueger gained equal billing with the longstanding industry favorite was considered significant.

One independent oilman who believes that Krueger will get industry support in both campaigns is John Newman of San Antonio, a Texas representative on the Interstate Oil Compact Commission.

"Krueger has led the fight for gas deregulation and he has led it beautifully," he says. "In the best interests of the country, he deserves our support and will get it."

Still, Tower is off to an early lead in the quest for contributions.

As a result largely of a $100 per plate dinner in Houston last month featuring former President Ford, he has already banked $315,000.

Krueger's first report on contributions due next week will show that he has received around $100,000. But he says he has also gathered more than $600,000 in pledges.

He has held a series of informal sessions with wealthy supporters in San Antonio, Houston and Dallas.A recent Dallas gathering included three prominent oilmen among hosts and recruited 18 volunteers pledged to raise $90,000.

Though Krueger becomes the first Democrat formally in the race, he faces potential opposition for the nomination from Barefoot Sanders, who ran a strong race against Tower in 1972 and Joe Christie, chairman of the Texas Insurance Board.

Both have reported they will make a decision on whether to run sometime in the fall.