UNITED NATIONS — The United Nations, and the way Americans relate to it, has become a “wedge issue” that could soon decide a presidential election, a pollster, Frank Luntz, said.

A center-right think tank, the Hudson Institute, commissioned Mr. Luntz’s national survey, which was released yesterday and found that while Americans are divided almost down the middle on their opinion of Turtle Bay, they have become less favorable toward it since the attacks of September 11, 2001.

According to the poll, a majority of Americans believe the United Nations is “no longer effective,” and if it cannot be reformed, it should be “scrapped altogether.”

Mr. Luntz, of Luntz, Maslansky Strategic Research, said the survey shows that Americans are “one scandal away from washing their hands” of the United Nations. A perceived U.N. failure to resolve issues like the Iranian nuclear standoff, he said, could also make Americans turn their back on the world body. Turtle Bay is on the verge of becoming “an issue that could win or lose” a presidential election, the pollster added.

Mr. Luntz said several U.N.-related issues crossed party lines.

Fifty-seven percent of the 800 telephone interviewees said they “agree” that if “the U.N. cannot be reformed and made more effective, it should be scrapped altogether and a more effective international organization should take its place.”Thirty-eight percent said they “disagree,” and 5% did not respond. Among Republicans, 69% agreed and 28% disagreed. But even among Democrats, the results were a virtual tie, considering the 3.5% margin of error: Forty-six percent of Democrats said they agree, while 50% said they disagree.

“That’s when you know that the issue transcends position politics,” Mr. Luntz said.

Support for the United Nations is strongest among Democrats, younger males, and in the Northeast, while Midwesterners are the harshest critics, the poll found.

Americans by and large support the United Nations, Mr. Luntz said, but the “no. 1 complaint is about corruption and the scandals.” Most interviewees, 49%, said the United Nations should concentrate on ending corruption and mismanagement, while 28% said it should promote human rights, and only 13% said it should address wars and military conflicts.

The most worrying numbers for the world body have to do with America’s 22% contribution to Turtle Bay’s budget. Thirteen percent said that contribution should be “increased,”while 71% said it should be “decreased.” Sixty-five percent said they do not believe America gets “good value” for the money it spends on Turtle Bay, and 64% of respondents who identified themselves as Democrats want to decrease America’s contribution to the United Nations.

In addition, 73% said they oppose the planned $2.8 billion Turtle Bay renovation, of which America will pay $600 million. Just 21% support the plan.

Mr. Luntz said his poll was designed to prevent bias. Generalized questions were asked first, with more particular ones later.