President Carter scored a double victory tonight in the Wisconsin and Kansas primaries that halted the week-old rally in Sen. Edward M. Kennedy's fortunes and drove California Gov. Edmund G. (Jerry) Brown Jr. out of the race for the Democratic nomination.

In bouncing back strongly from last week's twin losses to Kennedy in New York and Connecticut, Carter further strengthened his claim to renomination at the Democratic convention.

His campaign chairman, Robert S. Strauss, said the day's results "nailed down with some certainty the eventual outcome."

With 88 percent of the precincts in Wisconsin reporting, Carter led with 56 percent, Kennedy had 30 percent and Brown 12 percent. With 99 percent reporting in Kansas, Carter had 57 percent, Kennedy 32 percent.

Brown, who had gambled all his available resources on Wisconsin, told supporters here that "this will be the last contest in which I will participate in 1980."

Failing to score well enough to requalify for federal matching funds, Brown said, "It is obvious the voters have . . . given the verdict on my 1980 campaign. . . . It is difficult to look at reality and accept it as it is, but it is also a liberating thing."

Brown, who was as gracious and soft-spoken in defeat as he had often been harsh and abrasive in pursuit of the nomination, said it had become evident that "in some ways, my candidacy has gotten in the way of my ideas.

"The lesson I take is that the voters do not think I am ready to be president," Brown said, "and I accept that judgment."

But he clearly signaled that he hopes to be part of the Democratic Party's future. "We are closing the door on this particular phase," he said, "but it is the start of another phase."

Brown said he is "convinced I'm onto something" in arguing the country will face a future crisis that will force a decision between "policies that will lead to Depression and war" and a "shift of values to what I call an ethic of stewardship.

"I expected things to occur a little sooner than they have," he said, but he indicated that at age 41, he can afford to wait.

By his victories in Kansas and Wisconsin, Carter added another 70 delegates, bringing him to 848 of the 1,666 needed for nomination. With 41 new delegates today, Kennedy's total now stands at 445 1/2, and there are 27 1/2 uncommitted.

Wisconsin also suggested vote approval for Carter's handling of the latest phase in the continuing, confusing drama of the Iranian hostage crisis.

An ABC News poll said voters for whom foreign policy was the most important issue favored Carter by 62 to 33 percent over Kennedy in Wisconsin.

Among the 22 percent of the Democratic voters who said they made up their minds in the past two days, when Iran was dominating the news, Carter got 46 percent of the support, Kennedy 35 percent and Brown 18 percent. That reversed the pattern of most earlier primaries, which saw the late-deciders break to Kennedy.

Wisconsin and Kansas voters woke up today to find Carter on their television sets, reporting a "postive sign" in the decision of the Iranian regime to take custody of the American hostages from the militants who have held them for 150 days in the U.S. Embassy in Tehran.

Later in the day, it seemed less certain that the most recent strategy for gaining the hostages' release would succeed, but by that time, much of the vote in the two states had been cast.

Strauss said the results showed "we have straightened out the problems that caused the dip in the road last week in New York and Connecticut." He said he expected "other dips" between now and convention time, but none serious enough to cost Carter the nomination.

Kennedy stayed in seclusion at his McLean, Va., home, and let his brother-in-law and campaign chairman, Stephen Smith, extend congratulations to Carter on his victories.

Smith told reporters at Kennedy's Washington headquarters that the campaign had not been able to make a major effort in Wisconsin. But he predicted "a strong win" for Kennedy April 22 in Pennsylvania, and rejected any possibility of the senator's dropping out.

What was impressive about Carter's victory in Wisconsin was the strength of his support among all categories of voters. The ABC News survey of voters leaving polls showed the president beating Kennedy among Catholic and Protestant voters, union and nonunion families, and carrying rural areas, small towns, surburbs and cities. He beat Kennedy badly among moderate and conservative voters, and was sandwiched between Kennedy and Brown in a 39-33-27 percent split of liberal Democrats.

So pervasive was the sweep that Carter carried Madison, the state capital and home of the University of Wisconsin, long a liberal center, surrounding Dane County and its 2nd Congressional District. His victory was aided by a large Democratic crossover to support Rep. John B. Anderson in the Republican primary.

The personal character issues that have been submerged in New York and Connecticut rose up again here to plague Kennedy, as they had done earlier in New Hampshire, Illinois and the southern states.

Among those voting in the Democratic primary, 59 percent said issues were most important in their voting decisions, and 32 percent said they decided on the basis of the personal characteristics of the candidates.

The issue-oriented Democrats split this way: Carter, 40 percent; Kennedy, 38 percent; Brown, 19 percent.

Kennedy led among those most concerned with inflation and the needs of the poor and elderly, relfecting his campaign themes. Carter had an edge among those most concerned with foreign policy and holding down government spending -- a feedback from the voters on his budget-balancing and Iranian initiatives of the past week.

But his real edge came from those most concerned about the personal characteristics of a president. Carter won two-thirds of the votes of those most concerned with truthfulness, and 54 percent among those most concerned with fidelity to principle.

Although Wisconsin was a pioneer in the presidential primary system and has been the site of historic battles through the years, the 1980 Democratic contest did not take shape until the final days of campaigning.

For months, there was uncertainty whether the state would be allowed to select Democratic delegates through the primary this year. Wisconsin has a jealously guarded tradition of an "open primary," in which each voter is given the ballots of both parties and decides, in secret, which one to use.

The Democratic National Committee has adopted a rule for the 1980 convention banning "open primaries," and has been battling Wisconsin authorities on the issue. The Wisconsin Supreme Court ruled unanimously in favor the the "open primary" law, and while an appeal is pending in the U.S. Supreme Court, the Democratic National Committee has acceded to its use again this year.

The Carter supporters in control of the committee feared that any further fighting on the issue might cost the president votes in a state he barely carried in the 1976 primary and general election.

Until the March 25 Kennedy victories in New York and Connecticut, it appeared Carter would win Wisconsin again -- almost by default.

Kennedy had made but one visit to the state, and had only five paid staff people working here. Angie Martin, the Kennedy state coordinator, said that until the New York victory, "we really didn't have a campaign here." But the last week saw a frantic burst of Kennedy activity, climaxing in a two-day visit by the senator that wound up Monday night.

Faced with this fresh challenge, the Carter campaign sent in "vacationing" White House aides to bolster the 23-member staff that had been working out of seven headquarters around the state.

Vice President Mondale expanded his speaking schedule, and used his popularity among such traditional Democratic voting groups as union members, farmers and minorities to counter Kennedy's appeals.

The intensity of the Carter-Kennedy rivalry in the closing days cast a shadow on the campaign hopes of Brown. After failing to win any delegates in Maine or New Hampshire, the Californian pulled his underfinanced campaign together again in Wisconsin.

He spent most of March stumping here, while others were occupied in Illinois, the Northeast and the South. Brown focused his efforts mainly on Kennedy and liberal Republican Rep. John B. Anderson for support of students and other antiestablishment groups.

But Brown's planned campaign extravaganza -- a statewide telecast from Madison Friday night -- was marred by serious technical flaws which detracted from his message and contributed to the impression that his challenge was more unconventional than substantial.

Kansas, which was holding its first presidential primary this year, received relatively little attention from the Democrats. Brown ignored the state, and Kennedy did little more than make a swing late last week. Carter had the backing of most organizational Democrats and went into the race as a favorite, despite problems caused by falling wheat prices, and recent layoffs in some of the state's aircraft plants.