President Carter was renominated tonight by a Democratic Party convention drained of emotion by three days of platform and rules debates, and apprehensive about its prospects in the November election.

Carter's defeated challenger, Sen. Edward M. Kennedy of Massachusetts, immediately issued a statement congratulating the president, endorsing the Democratic platform and vowing to "support and work for the election" of Carter.

Kennedy said, "It is imperative that we defeat Ronald Reagan. I urge all Democrats to join in that effort."

The Kennedy statement of reconciliation was read to the delegates and the convention hall band played the party's theme song, "Happy Days Are Here Again."

Praised as a man of peace, prudence and practicality by the speakers who nominated and seconded him, Carter won his chance to become the first reelected Democratic president since Franklin Roosevelt in a roll call whose result had not been in doubt for at least two days.

With some strategic passes by some state delegations, the honor of putting Carter over the top went to Texas, which will be a main battleground in in the president's uphill battle against the Republican nominee. Virtually all of the Kennedy delegates stayed with the senator, despite being released from their commitment.

The completed roll call produced this tally: Carter, 2,129; Kennedy, 1,146.5 and others 53.5.

Afterwards, Lt. Gov. Thomas P. O'Neill III of Massachusetts, son of the House speaker and an ally of Kennedy, said the defeated candidate urged him to move for unanimous nomination of Carter. By voice vote, with a little grumbling from the ranks, the convention complied.

Carter watched the scene on television in his hotel room, where he was accompanied by his national campaign chairman, Robert S. Strauss of Texas, consumer representative Esther Peterson and Los Angeles Mayor Tom Bradley.

Right after the president's triumph, Kennedy telephoned him with personal congratulations.

First Lady Rosalynn Carter and other members of the family were cheering in Madison Square Garden when the decisive votes were cast just after midnight.

Democratic National Chairman John C. White, another Texan, came to the podium waving an early edition New York newspaper headlined: "It's Carter Again."

The two young men who are so close to Carter and had so much to do with his rise to the presidency tried to conceal their emotions behind a facade of cool professionalism. But at the moment of the president's convention triumph, both Hamilton Jordan and Jody Powell knew where they wanted to be -- with the Georgia delegation on the floor of Madison Square Garden.

Press secretary Powell, standing beneath the Georgia banner, was asked how it felt to have helped bring Carter to the moment of nomination for a second time. "Not bad," he replied. But tears glistened in his eyes, and when a reporter from Georgia asked the same question, the fierce sense of southern pride that is so much a part of the president's inner circle could not be concealed.

"Up until three years ago, we never had a president from Georgia," Powell said. "We're fixin' to have one for the second time, and I'm proud of it."

Jordan did not make it to the Georgia delegation in time for the moment of Carter's triumph. When the votes of the Texas delegation put the president over the top, Jordan came out onto the floor, but was engrossed by well-wishers and heard the Texas vote while standing beneath the banner of the Wyoming delegation. He finally pushed his way through to the Georgia delegation where, amid the wild floor celebration, he stood a few feet away from Powell to watch the scene.

Powell turned, and spotting his White House colleague, reached out his hand to Jordan and said, "Congratulations, I couldn't have done it without you."

They both laughed. But when Jordan was asked whether they were going to pull off another come-from-behind victory on Nov. 4, the look on his face hardened. "Yes," he said, "and it's going to be a lot easier than you think."

For many of the people on the convention floor, tonight's vote marked the end of a second long journey through the tortuous primary process that the Carter campaign has mastered. Anne Edwards, a young White House aide, said she was watching many of her friends on the floor during the vote.

"You look out and see the whips still whipping," she said. "A friend of mine works Maryland, and then you hear Maryland called and it's over. It's like saying goodbye to the campaign."

Nowhere was the process that now has twice brought Carter the Democratic presidential nomination better expressed than in the delegation from Iowa, the state that gave him his national political start in 1976 and the state where he first proved that he could beat the supposedly invincible Kennedy in 1980.

As the roll call began, Ed Campbell, the Iowa state chairman, stood on a chair and began calling out delegate names. Iowa, the state that began the process in 1976 and 1980, was taking one last poll of itself. And the final results were no different than they were at the beginning -- 31 votes for Carter, 17 for Kennedy and two uncommitted delegates voting for Sen. John Culver.

Carter was nominated by Florida Gov. Bob Graham as "a man of quiet wisdom and proven leadership" who "practices the politics of reality in a complex world where there are no easy answers."

Graham derided Ronald Reagan as "a man whose policies are based upon old newspaper clippings he carries around in his pockets."

Sounding an expected Carter campaign theme -- that Reagan is not capable of dealing with the difficulties of the 1980s -- Graham said the Republican nominee "proposes to practice the politics of nostalgia in a make-believe world whose problems are those of a small town in the 1920s."

Graham praised Carter for making energy policy his top domestic concern, for his actions in response to the Soviet invasion of Afghanistan and for his effort to bring down the inflation rate.

"Those decisions took courage to initiate," he said. "These decisions will take time to bear complete results. But even now, we're beginning to see the early effects of this quiet, determined courage."

In contrast, Graham said, Reagan says that "the solution is simply, that every challenge should be met with a saber-rattling confrontation."

"My friends, that's not simple -- that's simple-minded."

Graham said Carter's reelection is critical because "we frankly do not know what kind of issues we will face in the next few years."

"Will we be satisfied with a man of nostalgia and wishful thinking or do we want a man of substance and reality?" Graham asked.

Carter was the second candidate nominated, following a symbolic nomination of Rep. Ronald V. Dellums of California, a leader of the Congressional Black Caucus.

Dellums, a Kennedy supporter, came onto the podium and, before withdrawing, gave a speech echoing many of the liberal themes Kennedy had employed in his speech Tuesday night.

Warning that "you cannot defeat Ronald Reagan by moving to the right," Dellums told his fellow liberals to stay in the fight, promising, "We can win back our party and win back America."

Just before the nominations began, California Gov. Edmund G. (Jerry) Brown Jr., the only Democrat to be beaten by Carter in both the 1976 and 1980 nomination fights, appeared as an apostle of party unity.

Praising both Carter and Kennedy, Brown asked all Democrats to remember that Reagan "is ultimately accountable to the party of Nixon and Ford, the party of Hoover and Coolidge, the party of Harding and McKinley. That is not our party. That is not you."

Brown said the three-year, 30-percent, across-the-board tax cut that Reagan has advocated would give Reagan "90 times more actual tax relief than it does the average American."

Brown gave the anti-Reagan theme his own rhetorical twist when he said that even if Reagan had "his tax cut, his nuclear bombs, his breeder reactors and his superiority over Russian imperialism, I say it will be as verbal cellophane and an empty symbol when marshaled against the outraged enmity of the emerging 1 billion hungry people."

Both Brown and Graham acknowledged that the president faces an uphill task in defeating reagan, and both made strong pleas for party unity.

"We are going to need all of you to meet this challenge in November," Graham said. "He needs us as we need him," Brown echoed. "Victory is not assured, but it is within our grasp."

While it took Carter 18 months of nonstop campaigning to nail down the Democratic nomination in 1976, this year he spent exactly one day on the campaign trail: May 29 in Ohio.

But tonight the result was the same: a victory for Carter as gratifying and, in its way, as unexpected as the 1976 verdict.

Meeting again in Madison Square Garden, as they did four years ago, the Democratic National Convention delegates once again prepared to entrust their party's hopes to the peanut farmer from Plains, Ga., who this year also bears the title Mr. President.

Once again, the air in the home of the Knicks and the Rangers was rent with Rebel yells, as southerners celebrated the imminent victory of one of their own over the sophisticated city slickers.

In 1976, Carter was not supposed to have what it took to defeat such practiced Washington politicans as Scoop Jackson, Sargent Shriver, Morris Udall and Birch Bayh. But he did.

And this time, he trailed Sen. Edward M. Kennedy by almost 2 to 1 when the contest began nine months ago.

Tuesday night, Kennedy won the cheers and, some said, the hearts of the delegates with Carter himself called "one of the greatest speeches I have ever heard."

But tonight the too-often-dismissed Carter was certain to win the nomination.

Whatever else history may have to say about the 55-year-old Annapolis graduate, it will have to mark him as the supreme strategist in the nominating politics of the unbossed, open-caucus-and-primary era.

In December 1974, about to leave public office after four years as governor of Georgia, Carter announced for the presidency -- and people laughed or yawned.

But he and his young aides had figured out something the the smart Washington politicians had somehow missed: that continuous personal campaigning in the early caucus and primary states could build a volunteer organization strong enough to catapult an unknown into a front runner.

This year, Carter reached back to those networks of early supporters again, but added to his campaign machine elements attracted by the power of an incumbent president: mayors and governors eager for federal grants, teachers grateful for the flow of dollars and Cabinet status for education.

Together, they defeated Kennedy, the seemingly unstoppable heir to the most famous name in the Democratic firmament. and they did it with Carter barely stirring from the White House.

The decision that the president would not participate openly in his renomination campaign was the most controversial of the year. The president and his aides said it was justified by his need to work full time on the Iranian hostage crisis and, later, on the crisis caused by the Soviet invasion of Afghanistan.

While Carter said his "obsession" with these problems precluded spending time on politics, critics charged -- and some White House officials later acknowledged -- that he also hoped to focus voters' minds on the latent doubts about Kennedy's character and policy views.

Whatever the truth, the tactic worked. While Kennedy's side prevailed this week in many of the platform debates, Carter won what he went after -- renomination.

Unlike 1976, Carter's celebration this week is tempered by the knowledge that he is an underdog in the general election. The latest polls show him about 14 percentage points behind Republican nominee Ronald Reagan and only a few points ahead of independent candidate John B. Anderson.

Four years ago, Carter was the confident challenger to Jerry Ford, starting out with a comfortable lead over the problem-laden incumbent president. This time, the tables are turned on Carter.

It is Carter who has the burden of public frustration with the intractable problems of inflation and recession, of energy dependence and of the Ayatollah Ruhollah Khomeini's intransigence.

But the qualities Carter has demonstrated in his rise from peanut farmer to president -- his tenacity and single-minded determination, and his ability to rise to the challenge posed by a famous, favored opponent -- are the very reasons his supporters argue that he cannot be counted out in November.

For the first two days of this convention, Carter was secluded at Camp David, while his lieutenants here cracked the whip on his delegates to defeat Kennedy's desperate effort to budge them from their pledges. After the challenger quit, Carter yielded him the spotlight Tuesday to make his speech and gain a few more platform points.

But when the president came to town, he came as a man in command.

Air Force One landed this morning in nearby Newark, where Carter was greeted by a large delegation headed by one of his strongest supporters, New Jersey Gov. Brendan T. Byrne. The choice of Newark for the arrival was widely interpreted as a snub of New York Gov. Hugh L. Carey, who opposed the president in the critical "open" convention rules test Monday night.

From Newark, Carter flew by helicopter to Manhattan and went by motorcade to his headquarters hotel, where hundreds of supporters waited to greet him at a spirited rally.

Arriving to the chant of "We want Jimmy," the president wasted no time in paying tribute to his vanquished rival.

He said that Tuesday night, "after one of the greatest speeches I have ever heard," he called Kennedy to congratulate him on the performance.

From the rally, Carter went to a reception for some state and local officials who were a key to his primary victories and whose support in November will be crucial in a number of large, industrial states.

Again he promptly praised Kennedy's speech, saying "it will go a long way toward unifying our nation and guaranteeing a victory in November."

Previewing a theme he is expected to use in his acceptance speech Thursday night, the president said the general election campaign will demonstrate "the brutal difference" between the Democrats and the Republicans "in their concept of America now and their concept of our future."

"Let the Republicans try to explain some of the ridiculous attitudes they've already assumed and the promises they have made to the American people that can never be carried out," he said.

Carter told reporters he planned to meet with Kennedy. But for most of the day the president remained secluded in his hotel room, working on his statement for tonight on the party platform and on his Thursday acceptance speech.

Sources familiar with the acceptance speech said it is aimed beyond the walls of Madison Square Garden at undecided voters and even at those who may be skeptical or hostile toward Carter.

The sources said the speech has gone through four major revisions since the first draft was written after Carter return from the Venice economic summit in July.

The speech will invoke Democratic heroes of the past, they said, but will not attempt to capsule the Carter record of promises in single catch phrase. Basically, one who has seen the speech said, it is an argument that "I'm better than the other guy," focused not on the delegates in the convention hall but on the doubtful in the television audience.

While Carter was rehearsing his speech a reported six times today, Kennedy was enjoying an outpouring of praise for his powerful address Tuesday night.

His staff said hundreds of telephone calls and telegrams were received at his New York hotel and his Washington headquarters. The 175 wires handed to reporters as a "random sample" contained many more hints of a hoped-for future candidacy for Kennedy than they did pledges of support for Carter. Some excerpts:

"Keep the faith. Eighty-four only four years off," wired a supporter in New Orleans. "He said he would whip your ass. Now please don't kiss his" -- (Ashtabula, Ohio). "I urge you to support John Anderson, not Jimmy Carter" -- (New York City). "I am one supporter that would not ever vote for Carter after seeing the treatment you got" -- (Madison, Wis.). e"Splendid, Splendid. 1984" -- (Beverly Hills, Calif.).

This afternoon Kennedy lunched with his wife, Joan, at The Box Tree, an upper-bracket Manhattan restaurant where lunch for two runs more that $100. Afterwards he strolled the short distance back to the Waldorf Astoria, and while few ordinary New Yorkers could penetrate the security and media swarm around him, many of those who did urged him to try again in 1984.

Kennedy staff members, their spirits restored by the senator's stirring performance Tuesday, also were talking about the 1984 election.

"In a way, this last 10 months was an exhausting way to clear the path for 1984," said one senior Kennedy adviser. "But it will turn out it was worth it."

On his own night of triumph, Carter could indulge his vanquished foes such consolation as they could find in these thoughts.