The victory of Texas Gov. George W. Bush in the Iowa straw poll has ushered in a new phase in the Republican presidential contest that will be marked by his rivals' efforts to weaken him with increasingly strident attacks, several GOP officials said yesterday.

The lines of attack became clearer yesterday, with several opponents saying they would use the fall months to portray Bush as vague and evasive on critical issues, and lacking in the preparation and temperament needed to be president. Furthermore, they said they would seek to drive a wedge in what they see as his effort to simultaneously appeal to the broader electorate without offending the GOP's base of conservative voters.

Bush finished first in Saturday's Iowa straw poll with 31 percent of the vote in a nine-candidate field. While the Bush camp portrayed it as a significant victory, his opponents said it suggested weakness, noting that seven in 10 voters cast ballots for other candidates.

"At the end of the [straw poll], we literally had hundreds of people who came back to our tent and signed on to our campaign because they voted before the speeches," said candidate Gary Bauer, who finished fourth. "I think his generalities will not hold up for another six months."

Some rivals and critics also have pointed to this month's Talk magazine article profiling the Texas governor as a sign of his foibles. In the article, Bush, among other things, curses repeatedly and appears to mock a woman whose execution he allowed to go forth. Conservative columnist George Will wrote that it suggested "an atmosphere of adolescence, a lack of gravitas" and that the party would be hurt if on Election Day next year voters think of him as an "amiable fraternity boy, but a boy."

On the other hand, several opponents said yesterday they had no plans to make an issue of one question that has dogged Bush in recent weeks--whether he has ever used cocaine. Bush has steadfastly refused to answer, saying he would not play the Washington "gotcha game."

Bill Dal Col, campaign manager for Steve Forbes, who finished second in Saturday's Iowa contest, said conservative voters are wearying of Bush's fence-sitting. Forbes, he said, will continue to press Bush on how he would end abortion and promote school choice, among other issues, and insist on debates with Bush.

"The point is, the governor hasn't let it be known where he stands on things," Dal Col said. "He answers questions quite flippantly and arrogantly. And he sloughs off [criticism] when he doesn't know the difference between Slovenia and Slovakia, things that make a difference."

Bush has enjoyed the luxury of running a campaign focused as much on a general election audience as on the more conservative party activists who turn out for primaries and caucuses. But in the months ahead, he's likely to face criticism from the right, which will test his commitment to the conservative issues that many in his party demand.

Mindy Tucker, a Bush campaign spokeswoman, said yesterday that targeting Bush with negative attacks would backfire. She rebutted criticism that Bush has been vague, calling it "misperception gone wild." She said Bush, who last month outlined his plan for government to cooperate with faith-based groups to solve social problems, has several more specific policy speeches--including education, economic policy and defense--planned for the fall.

Brian Kennedy, a top adviser to Lamar Alexander, who pulled out of the race yesterday, said Bush "came closer to Earth" with the results in Iowa and that in sharing the stage with his rivals may have lost a little of the halo effect around his candidacy.

Like others, Kennedy pointed to Bush's speech to the party activists on Saturday, which received a lukewarm response. "One thing Bill Clinton and Ronald Reagan had in common is that when they were under the red-hot lights, in the big moments, they were always able to lift their performance to the next level," Kennedy said. "This was one of those moments. . . . He didn't deliver a performance that rose to the occasion."

Kennedy added that "those who choose to attack will attack from the right and that will make it more difficult for him to run a general election campaign reaching out to the center until the primaries are over."

Bauer said he will challenge Bush not just for being evasive, but for being on the wrong side of issues. He said Bush's assertion that he would not insist on nominating antiabortion judges, for instance, runs counter to mainstream Republican philosophy.

Bauer also has criticized Bush publicly for the Talk interview. "Overall, I've been pro-capital punishment," Bauer said. "But in all of the years I've been debating that subject, I don't ever recall another official having sunk to mocking the person he put to death. It's hard for me to understand what could have been going through his mind when he did that."

Marilyn Quayle told an Arizona newspaper that the caricature of her husband, former vice president Dan Quayle, was more appropriate of Bush and that "the guy never accomplished anything, everything he got daddy took care of."

The Bush camp has been trying to deflect criticism over the Talk article.

In a news release last week, for example, the campaign said Bush and aides did not recall him using bad language, but "if it was, Gov. Bush believes it was inappropriate."

Conservative activist Grover Norquist, a Bush supporter, argued yesterday that there are fewer ideological differences among the GOP candidates than in any primary race in decades. Conservatives, he said, understand that Bush's positions on controversial social issues are essentially the same as every other candidate's.

"What you've got is people arguing that Bush doesn't talk about abortion as much as the next guy," Norquist said. "This is why they're not getting traction with this criticism. So you end up with stuff like, 'He swears too much,' which might be perfectly legitimate, but won't lose you the Pennsylvania primary."