Some of the District of Columbia's most prominet bankers, developers, realtors and other corporate officials are hedging their bets on the city's crucial Sept. 12 Democratic mayoral Primary by making donations to more than one of the principal contenders.

Most of the contributions from business executives and their companies have gone to City Council Chairman Sterling Tucker and Mayor Walter E. Washington, but in a few instances the business officials also have given money to the third major candidate, Councilman Marion Barry.

Some of the business officials say their double or triple contributions are an attempt to show their corporate presence in the city, no matter who the mayor is during the next four years, or gain a little access to the mayor's ear when they have a problem. Other business executives say they feel it is their civic duty to give money to the candidates so they have enough money to put on a respectable campaign.

As it turns out, any political contributor attempting to give to a likely winner would have a difficult time choosing a candidate. Officials in all three campaign say that with a month to go to election day their polling and canvassing tells them that the race is exceedingly close and still can be won by any of the three.

Some of the business contributors made donations to Tucker and Barry earlier in the year and now are giving to Washington, a fact the mayor says shows that some old support him after considering Tucker and Barry.

The mayor said at a fund-raise at the Georgetown home of lawyer and socialite Steve Martindale that some contributors have told him they contributed earlier to Tucker and Barry because "they didn't think I'd be runing."

But now the mayor said the Tucker and Barry givers are contributing to him because he tooks like a winner.

"You know that's so," the mayor said with a hearty laugh as he slapped a reporter on the shoulder.

One effect of the double or triple donations is to make the current mayoral campaign easily the most expensive in the city's brief experience with limited home rule powers. Four years ago, when spending was limited to $200,000, Washington reported raising close to that and his chief Democratic challenger, Clifford Alexander, about half that.

But already this year. Tucker has raised a reported $208,116. Barry $182,697 and the mayor $130,502. a total of more than $520,000.

While all three candidates are, of course, glad to collect money wherever they can get it giving equally to all three could tend to negate the effect of a donation.

Ivanhoe Donaidson. Barry's campaign manager, said he conisders $1,000 contributions to all three the same as not giving at all. Such contributors are "not prepared to stand behind a commitment and let it ride," Donaldson said.

The Washington. D.C. Area Tucking Association Inc., the Shannon & Luchs Co. real estate firm and the D.C. Medical Society's political action committee (know as DOCPAC) gave all three candidates $1,000.Meanwhile, the John R. Pinkett Inc. real estate firm gave each of the candidates $500 and its president, Flaxie M. Pinkett, gave the mayor's campaign another $1,000.

Developer Oliver T. Carr Jr. gave Tucker $1,000 and his company donated $1,00 to the mayor. Joseph H. Riley, the chief executive office of National Savings and Trust Co., gave $500 apiece to Washington and Tucker. The Potomac Electric Power Co. gave $1,000 to Washington and through a political action committee, $2,000 to Tucker. The Woodward & Lothrop department store chain gave $2,000 to tucker through a political action committee and $500 to the mayor.

Some of Tucker's biggest funancial boosters have been members of the Howar family real estate and development ventures. Early in the campaign, Paymond J. Howar said he called family members together and, at Howar's urging, they contributed a total of $6,750 to Tucker's campaign.

At the time, Howar dismissed the possibility of contributing to the mayor's campaign, but now a Howar family partnership has contributed $750 to the mayor.

Howar said he still supports Tucker and thinks he is ahead in the race. But, he said. "I frankly felt it appropriate" to contribute to the mayor's campaign. "I do have an appointment from him" to the D.C. Rent Control Commission. "Also, I've known him for a long time," Howar said.