The Washington Post fund-raiser held Wednesday night for Texas Democratic senatorial candidate Robert Krueger was no ordinary affair.

It was held in the Watergate apartment of presidential confidant Robert S. Strauss, the special trade representative and former inflation czar.

Those in attendance - about 80 in all - comprised a select group. Most of them were from the business community and many of them represent energy companies.

The price of admission: $1,000.

The guests were served up the ordinary buffet fare of such gatherings: roast beef, pate, steak tartare and drinks.

They were also offered the president of the United States. He gave a speech, mingled with the guests and didn't leave for almost an hour. The normal press pool that accompanies him almost everywhere was left standing outside trauss' door.

And the take from the two-hour affair, according to Krueger's office, was about $97,000, no ordinary sum. "It really worked out well," said Loyd Hackler, a prominent Democrat, a TexanK friend of fellow Texan Strauss, and head of the American Retail Federation. He and Democratic National Committee chairman John C. White organized the fund-raiser.

"Selling Carter," Hackler said, "ain't a bad way to have a fund-raiser."

The race between Krueger and his opponent, incumbent Republican John Tower, has been accompanied by considerable insecurity among energy interests. Both men have supported industry positions in Congress. As a result, oil and natural gas interests along with numerous other business groups have contributed heavily to both campaigns.

Strauss said those invited were "mostly business types and professional people . . . mostly with Texas backgrounds and interests. They were people obviously of some substance," Strauss said, "or they wouldn't be albe to afford it. "It wasn't the regular Washington lobby that came."

According to a list of those attending or committed to attend, it included representatives of Brown and Root, the oil service company, Dresser Industries, the company that makes the oil drilling equipment that Soviet Union wants to buy, Marathon Oil, the Independent Cattlemen's Association, APCO Oil, Grumman Aerospace, Sakowitz Department Stores, LTV Corp, the National Rural Electric Cooperative, General Electric, the Dana Corp, and numerous lawyers and numerous Texas businessmen.

"Almost the entire group had some sort of tie-in with energy," said John Archer, Washington representative for Brown and Root. And almost "everybody had a chance to visit with the president for a while."

Strauss said President Carter spoke about the "significance of the Krueger campaign, saying that he had found him to be an extremely good ally when he was an ally and an exceedingly formidable adversary when he was an adversary, for example, with respect to energy." (Krueger has worked hard for immediate dregulation of natural gas.)

"The president also pointed out that it was the first time he'd ever gone to a private fund-raiser like this one," Strauss said.

Strauss said he had neither solicited funds for the event nor chosen the people to be invited. He said Hackler, White and Hackler's son, Craig, had done that.

"It was a nice party," he said. "In good taste. Nothing fancy."