Texas Gov. George W. Bush's victory in the Iowa straw vote triggered a new round of criticisms from his Republican rivals today and persuaded one of them, former Tennessee governor Lamar Alexander, to give up his bid for the 2000 presidential nomination.

Alexander, who never stopped campaigning after his first try to be the GOP standard-bearer fell short in 1996, is expected to withdraw as early as Monday in his home city of Nashville. He finished sixth among nine active contenders in the popularity contest here that drew a record crowd of more than 24,000 Republicans for the first -- and most significant -- contest before the real delegate-selection process begins next winter.

Alexander said on NBC's "Meet the Press" that there is "a powerful force out there to nominate George W. Bush, and there's a powerful force . . . to have a contest." But he added, "I'm not sure I did well enough last night to be part of it. . . . I'm obviously disappointed. I need to be honest about that. And I'm going to . . . make a decision in the next day or two about whether to go forward."

Bush won the straw vote with 31 percent of the total, followed by publisher Steve Forbes with 21 percent, former Cabinet member Elizabeth Dole with 14 percent, former Reagan White House aide Gary Bauer with 9 percent and conservative commentator Patrick J. Buchanan with 7 percent. Alexander was next with 6 percent, followed by former ambassador Alan Keyes with 5 percent, former vice president Dan Quayle with 4 percent and Utah Sen. Orrin G. Hatch with 2 percent.

The only other contender, Arizona Sen. John McCain, dismissed the straw vote as "a joke" and hinted strongly today that he will also boycott next winter's Iowa caucuses, where the delegate selection process actually begins.

Saturday's Iowa Republican fund-raising event has no effect on the delegate contest but served as a test of the candidates' organizational strength and personal appeal. Within hours of rolling up a total vote three times as large as that of any previous winner, Bush came under verbal assault from many of the trailing candidates who appeared on Sunday talk shows. The Texas governor let surrogates and staff members defend him against charges that he was insufficiently clear or simply wrong about an array of issues from abortion to China to Kosovo -- and maybe was too inexperienced to trust with the nomination.

Forbes, who spent more than anyone else on the straw vote and finished 10 points behind Bush, pressed his demand for debates this fall and said the Texas governor has "a rather mixed" record on taxes and other issues. "The American people are tired of having the vague generalities and spin," Forbes said on ABC's "This Week."

"The only way the Republican Party is going to win that general election is if we have a clear, lucid, inspired message," he added.

Under questioning, Forbes refused to apologize for the 1996 presidential primary ads he ran attacking Robert J. Dole and hinted he was prepared to be as tough on Bush's record. But Michigan Gov. John Engler, a leading Bush supporter, told reporters here, "Steve Forbes will implode if he does that."

Third-time candidate Buchanan was particularly caustic about Bush. On NBC's "Meet the Press," Buchanan claimed that even though he was edged out of fourth place in the voting by Bauer, "that auditorium erupted in howls [and] cheers for me when I denounced policies . . . that Governor Bush supports."

Buchanan's list of disagreements included Bush's support for normal trade relations with China, his endorsement of President Clinton's decision to wage air war on the Serbs in Kosovo, his support for liberal immigration policies and "a life policy on which Governor Bush has shown himself to be utterly indifferent to the right to life." Bush has said he would not demand that his judicial appointees be antiabortion.

Karen Hughes, Bush's communications director, rebutted the charge on abortion policy in two network appearances. Hughes also reiterated the governor's determination not to answer questions about possible drug use earlier in his life, saying, "We are not going to chase unfounded rumors and unproven allegations."

Bauer also went after the Texas governor on "Meet the Press," saying Bush and Vice President Gore "are like one candidate." Citing the China trade issue, the defense of Taiwan and even their receipt of Hollywood campaign funds, Bauer said, "Their positions are virtually identical."

But Bauer and Buchanan diverged sharply on the question of loyalty to the Republican Party. "I expect the Republican Party to represent my values when we get to Philadelphia [site of next August's Republican National Convention], and I'm not going to have any problem, I don't believe, in what the outcome is going to be there," Bauer said.

Buchanan, on the other hand, declined to pledge that he would support Bush if he is the nominee: "I don't know where I'm going to be in August of the year 2000, so I'm not going to make any statement like that. . . . I'm going to follow my star. . . . If my party is going to move off in a different direction, fine. But it goes in that direction without me."

There has been speculation that Buchanan might jump to the Reform Party and seek to win its nomination and the $12.6 million in federal funds its candidate would get on the basis of Ross Perot's showing in the 1996 election.

Buchanan acknowledged that the Reform Party "is agnostic on social issues," and its highest-ranking elected official, Minnesota Gov. Jesse Ventura, "is very, very liberal" on those issues. "I believe in these issues because I'm a Christian and a Roman Catholic," he said, adding that he was confident he would not face discrimination if he entered Reform Party ranks.

Buchanan said he will stay in GOP politics, at least for now, but on "Fox News Sunday," he spoke as if he did not think his prospects in the Republican race were very bright. The field "is much tougher" he said. Bush's speech to the jammed field house at Iowa State University was "altogether unexceptional," he said, "but they are hungry for a winner. . . . It makes what I did in 1996 much more problematic."

Elizabeth Dole, who did not commit to appear on the Sunday broadcasts until after she achieved her third-place finish, called it "a strong victory" against two candidates who probably spent $2 million to $3 million between them to win the straw poll.

She said she was particularly heartened by the participation of many women and young people who said they were newcomers to GOP organizational politics. Managers of rival campaigns also said that she had begun to prove that the crowds she has been drawing as the first serious female presidential candidate are not just curious but are prepared to work and vote for her.

But Dole also encountered her baptism of fire on "Meet the Press." Asked how she would keep the promise she made in her Saturday speech to shut down illegal drug traffic from Mexico, she said only that "there are a number of options" a president could consider after deploying "the power of diplomacy." Asked whether she agreed with the Kansas Board of Education's decision to strike evolution from the school curriculum, she said -- as Forbes did on ABC -- that she would leave it to the states.

When she repeated that answer and the assertion that "I am a person of strong faith" on CBS's "Face the Nation," she was asked if she were a "creationist" and if she believed literally in the Biblical story of creation. "I am a person of strong faith," she said again, "but I would leave it to the states to decide."

Despite finishing far back in the pack, Quayle told Fox News that he is "absolutely not" following Alexander to the sidelines, and expressed confidence that by the time the contest reaches New Hampshire next February, "I will be the alternative to George Bush."

Quayle aides said his mailing list of contributors has continued to be productive and he will have at least $1.8 million in matching funds available next January. Quayle took his own modest jab at the son of the man who had selected him for the vice presidency, noting that while Gov. Bush talks of the time before his 40th birthday as the period "when I was young and foolish," he, Quayle, had been elected twice to the House and twice to the Senate by that age.