While nominee-waiting Ronald Reagan built bridges to constituencies of blacks, women and unionists for the fall campaign, the delegates to the Republican National Convention tonight sealed their approval of his conservative platform and heard a series of sometime Reagan skeptics assert that he would be a vast improvement on Jimmy Carter.

Former secretary of state Henry A. Kissinger -- a longtime critic of Reagan's foreign policy credentials -- came before the convention to hail the former California governor as "the trustee of our hopes" for relief from the "feeble and apologetic" diplomacy of the Carter administration.

House Minority Leader John J. Rhodes of Arizona, taking the gravel as permanent chairman, continued the critical focus on Carter's "pretense and posture" on the Iranian hostage question, a focus begun Monday night by former president Gerald Ford.

Rhodes, former presidential contender John B. Connally and other speakers also dwelled on the theme of Democratic disunity, quoting Carter challenger Edward M. Kennedy lavishly in derogation of the president.

While they were busy encouraging the Democratic feuds, Reagan spent much of the day in his headquarters hotel, hand-holding with representatives of groups that have been hard to enlist in his campaign.

The most important of the meetings was with a delegation of women, angry that the platform that was formally approved tonight omitted the Republicans' past endorsement of the Equal Rights Amendment.

The meeting went well. Mary Louise Smith, the staunchly pro-ERA former national GOP chairman, said "we came away feeling good" about Reagan's promises to seek out women for high federal appointive jobs and to root out state and federal statues that discriminate against women -- even though the standard-bearer did not budge from his personal opposition to ERA.

When the platform came to the floor tonight, there was only the briefest flicker of rebellion from supporters of ERA and abortion rights. John Leopold, a Hawaii delegate, said his state wanted to suspend the rules to open those sections to debate.

A Massachusetts delegate seconded the motion, but when he said his state's delegates had voted only to ask for a roll call on the issue, he was ruled out of order. No other states seconded the motion, and with the rules requiring five states to put the question to a vote, that was the end of the effort.

Once the platform was out of the way, the convention began to pick up the pace and drama that had been missing.

Nancy Reagan, the prospective nominee's wife, made her first appearance in Joe Louis Arena and was greeted with a standing ovation. For a time, the box she was escorted to was shared by Elizabeth Taylor Warner, wife of Sen. John Warner of Virginia, one of the evening's speakers.

They were watching when NAACP President Benjamin Hooks made an unscheduled appearance on the podium.

Hooks, sounding a plea for the disadvantaged seldom heard here, reminded the delegates that one-fourth of the nation's blacks live below the poverty line, and called for support of social programs ignored or rejected in the GOP platform.

Hooks did what the delegates were unwilling to do: he asked the convention to reexamine the platform positions on ERA and abortion. On the latter issue he said, "Whatever your personal position might be, we at the in NAACP [believe] that any rights and options which are available to the rich must be available to the poor."

Hooks' appearance was a last-minute concession to the black delegates at the convention. He had criticized Reagan for passing up an invitation to speak at the NAACP convention last month, and GOP Chairman Bill Brock quickly decided that it was prudent to accept the suggestion that Hooks be invited here.

Reagan, who had minimal black support in past state and national campaigns, made a gesture toward that constituency by appearing before a reception for the black delegates and vowing to see that "everybody has the price of admission to go through," the doors that civil rights statutes have opened.

Through an irony of scheduling, the next major speaker after Hooks was Sen. Barry Goldwater of Arizona, the 1964 presidential nominee whose opposition to those civil rights bills split the party 16 years ago.

Goldwater, frail and silver-haired, was given a hero's welcome when he came on stage. He was using crutches after surgery for a persistent hip problem. The delegates cheered both his physical gallantry and his role as the early apostle of the conservatism that Reagan has come to personify.

Goldwater's speech was 100-proof 16-year-old political firewater.

Accusing the Democrats of making the United States "a second-rate power," he said, "if we had had leadership worthy of the name, Vietnam wouldn't have lasted more than a few days. If our leaders had displayed the guts and courage our country is noted for, no country in the world would ever have taken hostages from us."

The Arizona senator, mopping his brow and complaining of the heat in the hall, concluded his speech with a plea that Republicans avoid the internal bickering that blighted his chances in 1964.

"If we're not happy with every dot and comma of this platform, all right," he said. "Let's live with what we've got that we like. Let's have a little less carping, a little less nitpicking," and avoid "thousands of interpretations of morality and conservatism."

About 45 minutes after Goldwater finished, with the clock moving toward midnight and the convention far behind schedule, a well-planned demonstration greeted the younger-generation conservative hero, Rep. Jack Kemp of New York.

The onetime pro football quaterback has emerged as the favorite of delegates who want Reagan to complete his ticket with an ideological soul-mate, and the arena blossomed with thousands of placards proclaiming the virtues of a Reagan-Kemp combination.

Kemp, principal sponsor of the proposal for three years of deep cuts in the tax rate that has become the heart of Reagan's economic plan, drew repeated cheers as he predicted a "tidal-wave" Republican victory "as powerful as the one that hit in 1932" and made Democrats the majority party.

"For the past 25 years," Kemp said, "the Republican Party has been the minority party in government. But it is clear today that we represent the majority philosophy of the American people. In November, we will convert this philosophic majority into a governing majority -- in the White House, in the Congress and throughout America."

Kemp asserted -- as he has done in speeches across America and in a best-selling book -- that Republicans can win converts in union and blue-collar familes by becoming identified as the party of economic opportunity.

That Reagan is interested in those votes was indicated when he met earlier today with 19 auto workers and told them he would aid that ailing industry by easing the federal safety and environmental regulations he blames for some of its problems.

It was almost Wednesday when Kemp was followed to the platform by Kissinger. There had been rumors that conservative critics of detente would demonstrate against the former secretary of state -- or at least boo.

But only cheers could be heard, with Nancy Reagan leading the standing ovation, signaling a rapprochement that had been formalized at a meeting between Kissinger and her husband earlier in the day.

That meeting was designed not only to end the personal feud between the two men but to send a message to the eastern foreign policy establishment that Reagan was open to its influence, too.

Reagan remarked to reporters after the meeting that his differences with Kissinger had been exaggerated, and Kissinger -- in his speech to the convention tonight -- reciprocated with a stinging attack on Carter's foreign policy record.

Asserting that the administration "has managed the extraordinary feat of having at one and the same time the worst relations with our allies [and] our adversaries and the most serious upheavals in the developing world," Kissinger said: "Another four years like the last four will make disaster irretrievable."

He said that while disruptive forces were inevitable in the world, Carter had multiplied their adverse consequences by "a philosophy of abdication . . . allied to a diplomacy of incoherence."

"What are foreign leaders to make of a policy that first proposes to demilitarize the Indian Ocean and now seeks bases in all its corners?" Kissinger asked. "That offered our allies a neutron bomb and then withdrew it? That promised in 1976 to cut our defense budget, canceled or delayed every strategic program it inherited, and now fiddles with figures to pretend an increase? That first called Iran an island of stability and then dithered while it slid into hostility?

"That first ridiculed the need of a policeman in the Persian Gulf and then extended our own defense commitment to the entire area? That accepted a Soviet combat brigade in Cuba, stood by while Cuban troops with Soviet officers intervened in Ethiopia, and then was "shocked" by the Soviet invasion of Afghanistan 20 months after it ignored a communist coup there?

"That has vacillated between threats and renunciations of force while 53 Americans -- representing us -- have been held captive by so-called students?"

Kissinger's reference to the Iranian hostage situation picked up a theme enunciated by Ford Monday night and given further political point by permanent chairman Rhodes tonight.

The Arizona congressman said Carter's response to the hostage crisis has been determined "by the political calendar."

"Who will forget the Tuesday morning of the Wisconsin primary when the president . . . promised us an end of the hostage crisis?" Rhodes asked. "Who will forget the morning after the Wisconsin primary this promise was ignored?"

John R. Connally, another of the night's speakers, found himself playing a familar role: quoting one Democrat against another. Just as he did when he campaigned for Richard M. Nixon in 1972, quoting Hubert H. Humphrey against George McGovern, the former Texas governor and former Democrat reached back into his old party for oratorical ammunition.

"All of us who challenged Gov. Reagan for this nomination are united behind him," Connally said, conveniently ignoring Republican-independent John B. Anderson. Reagan "is that kind of opponent . . . that kind of leader," he added.

"On the other hand, our opponents are anything but united." And then Connally quoted some of Kennedy's comments on Carter -- that he "doesn't know the first thing about running the economy," that his "foreign policy is out of control," his "inflation policy . . . a calamity."

"We agree with Sen. Kennedy that we need a new president," Connally proclaimed. "We need Ronald Reagan."

What the delegates did not need after five hours of oratory -- the convention manages belatedly decided -- was the "keynote address" that was to have been given by Rep. Guy Vander Jagt of Michigan, chairman of the Republican Congressional Campaign Committee and a dark-horse vice president hopeful.

Vander Jagt, a Yale-trained preacher-politician, had broken with custom by telling officials he would deliver his speech without a prepared text, and now he will have to wait until Wednesday for inspiration to strike.

The keynote had been bumped from its traditional Monday night spot by party leaders' desire to accommodate former president Ford's wish to be the leadoff speaker -- on his 67th birthday. Tonight, it was shoved off the program by the abundance of warmup speeches.

In becoming the first party in modern history to schedule the keynote speech just before the climactic presidential nomination roll call, the Republican shed their image of stodginess and showed themselves almost as innovative as the Democrats were in 1972, when they put the acceptance speech by George McGovern on the air so long after midnight that, as he later said, "it was prime time in Guam."