Full voting representation in Congress for District residents has broad support and little organized opposition in the Senate, but nearly half of the senators have not made up their minds on the question, according to an informal poll by The Washington Post.

The Senate Judiciary subcommittee on the Constitution began hearings on the bill yesterday, and Sen. Edward M. Kennedy (D-Mass.), its chief sponsor, said "simple justice" requires passage. The measure passed the House March 2 by the needed two-thirds majority. The Senate is expected to vote on it late this summer.

Sen. Birch Bayh (D-Ind.), the subcommittee chairman, said the citing by proposal supporters of the theme "taxation without representation" was especially appropriate yesterday, the last for filing 1977 federal income tax returns. Bayh, one of six senators who spoke in favor of the bill, cited the "living paradox" of District residents who must pay those taxes "but are denied the basic right that goes along with paying taxes, the right to be represented."

Of the 93 senators responding to The Post telephone survey, 32 said they favor, or lean toward the bill; 18 oppose it, or lean toward opposition, and 43 are undecided.

Senators favoring the legislation include 22 Democrats and 10 Republicans of wide philosophical and geographicial interests. Co-sponsors of the bill in addition to Kennedy and Bayh include Sen. Barry Goldwater (R-Ariz.) and both Maryland senators, Republican Charles McC. Mathias and Democrat Paul S. Sarbanes.

Opponents include Senate Minority Leader Howard H. Baker Jr. (R-Tenn.) and both Virginia senators, Independent Harry F. Byrd Jr. and Republican William L. Scott.

Results of The Post survey are in line with findings of another informal poll by the national office of the League of Women Voters which identified 22 strong supporters, seven "hard-core" opponents and a majority undecided.

Elena Hess, executive director of Self-Determination for D.C., the coalition lobbying for the measure, said not enough senators have "focused sufficiently" on the details to predict its chances of passage. Many senators said they have been pre-occupied with the Panama Canal treaties debate, and have not had time to study the District matter.

"We have a reasonably good chance," Hess said, "worth making a good effort." She added, however, that House approval last month was a moral victory and means that "defeat in the Senate (this year) would not be a permanent setback."

Scott, who is a member of the subcommittee, predicted that "this legislation won't receive the two-thirds vote in the Senate, and if it does, it won't (win ratification) of three-fourths of the states. No one should be disillusioned about that."

Bayh, apparently riled by Scott's remark, said, "We're not just going through the motions. We're making a serious effort to move this through the committee, but if we can't, we'll move the House resolution."

(Using a parliamentary tactic, supporters of the idea have placed the House-passed version on the Senate calendar, assuring that it will be brought up for a vote before the end of this year.)

Sen. Edward W. Brooke (R-Mass.) said his testimony in support of the bill was "intensely personal." A native of Washington, and graduate of Dunbar High School and Howard University, Brooke noted that if "I had stayed in my hometown, I couldn't have been a senator."

Scott suggested to Brooke that "if you lived in Virginia, you might have my seat," to which Brooke replied to his fellow Republican, "I couldn't think of anything better."

Sen. Thomas F. Eagleton (D-Mo.), chairman of the Senate subcommittee on the District, said a letter he, received in 1971 from a Washington mother "did more to shape my thinking than a million words." The woman said her son had been killed in Vietnam, in a war whose policies were determined without her voice or vote.

Eagleton told Scott he could "name nine states that would promptly ratify out of a sense of fundamental fairness." Eagleton named Alaska, Wyoming, Navada, Delaware, North Dakota, South Dakota, Montana, Idaho and New Hampshire, saying all have few residents than the District.

Sen. James A. McClure (R-Idaho), an opponent, protested that his state now has more residents than Washington. He testified that "to insure that the District gets no special favors not accorded to cities of comparable size," he is prepared to introduce an amendment that would grant senatorial and congressional representation to all cities with populations equal to or greater than Washington.

McClure named 11 cities, including Indianapolis, to which Chairman Bayh answered, "The people of Indianapolis already have representatives," and that he was one of them.

"The best proposal," McClure went on, "is to return the nonfederal District land to Maryland."

Mathias followed McClure as a witness, and said he "can't take seriously" McClure's idea of retrocession. But Mathias said he detected "progress" on the issue because "proponents and opponents agree it is wrong for 750,000 residents not to have representation in Congress. That was not always the case."

John M. Harmon, an assistant attorney general, appeared as a witness "to express the strong support of the president and his administration" for the proposal.

Kennedy urged the committee to "smoke out unfair and disgraceful arguments sometimes found lurking in opposition . . . fear that the new senators may be liberals or Democrats or blacks. Such arguments cannot stand the light of day. They are unworthy of the Senate or the nation."

The District's nonvoting delegate to the House, Walter Fauntroy, sat in the front row of yesterday's hearing, but did not testify. Fauntroy has been carrying the message for full voting representation wherever he travels, whether as a member of the House Black Caucus, board member of the Southern Christian Leadership Conference or guest speaker as a member of Congress.

Part of the strategy of supporters is to put pressure on senators who have-large numbers of blacks in their [TEXT OMITTED FROM SOURCE]

Supporters say that strategy may have been responsible for the support of Sen. Ernest F. Hollings (D-S.C.) and the hope that his colleague, Sen. Strom Thurmond (R-S.C.), who faces reelection this year, will soon announce his support.