WASHINGTON — Jewish organizations are suddenly muzzling their criticism of presidential candidate Pat Buchanan for fear of losing their nonprofit status if they get involved in partisan politics or electioneering.

It is "difficult to know how far you can go and where exactly you have to stop," said an attorney for the Anti-Defamation League.

The Internal Revenue Service can strip a nonprofit organization of its tax-exempt status if it determines that the group engaged in election politics, the attorney said, adding that the IRS "does not provide a lot of guidance."

Buchanan left the Republican Party this week, announcing that he will seek the Reform Party's presidential nomination.

Officials at Jewish organizations such as the ADL and the American Jewish Congress, which have publicly criticized Buchanan's views in the past, would not discuss Buchanan's party switch. As nonprofit, non-political groups, those officials said, they could not comment on such matters.

Prior to his party switch, Jewish groups were publicly criticizing Buchanan's recent assertion that Nazi Germany posed no threat to the United States and that America did not have to enter World War II.

In announcing his decision and unveiling his agenda Monday to several hundred supporters chanting "go, Pat, go," Buchanan said the United States should phase out foreign aid, curtail its intervention overseas and implement a "timeout" in legal immigration.

It was a "very difficult day" for the Jewish groups that could not respond, one Jewish activist said.

The relative silence illustrates the delicate line Jewish groups — which because of their nonprofit status cannot engage in partisan politics or electioneering — have to walk when it comes to taking on candidates whose views with which they disagree.

Phil Baum, executive director of the AJCongress, noted that the group's recent half-page ad in the New York Times denouncing Buchanan's writings did not refer to the presidential election. At the time of the ad, Buchanan was seeking the Republican presidential nomination.

After Buchanan's book, "A Republic, Not an Empire," came out last month, the ADL put out a news release saying that "we find it extremely disturbing that Pat Buchanan continues to find mainstream political acceptance when his views place him far outside the mainstream."

The release did not mention that Buchanan was seeking the Republican nomination, but it did say that it had asked all the other Republican nominees to "denounce Pat Buchanan's anti-Semitism and bigotry."

Buchanan, a conservative columnist who ran for the Republican presidential nomination in 1992 and 1996, has long been accused of anti-Semitism by columnists, politicians and Jewish organizations. It is a charge he denies.

This week the ADL put out a backgrounder on the Reform Party itself and two of the party's activists, Fred Newman and Lenora Fulani, whom the ADL said have espoused anti-Semitism in the years they were involved with the now-defunct New Alliance Party.

It also has a "special report" on its Web site entitled "Pat Buchanan: In His Own Words."

Gail Gans, director of the ADL's Civil Rights Information Center, said that since it is classified as a 501c(3) by the IRS, the group can't appear to be supporting or opposing individual candidates but can discuss issues within the political parties.

Representatives of Democratic and Republican Jewish groups, as political activists, do not have to be as restrained.

Ira Forman, the executive director of the National Jewish Democratic Council, said Buchanan "will have a platform to spew his anti-Semitism and other xenophobic policies" if he wins the Reform Party nomination.

"You don't have the luxury of ignoring this guy anymore," Forman said, noting that Buchanan, if he is the nominee, will have access to nearly $13 million in matching federal funds and could be included in the presidential debates.

However, Matt Brooks, the executive director of the Republican Jewish Coalition, cautioned against making Buchanan into a Jewish issue.

"Pat Buchanan is an American problem, not a Jewish problem," he said.

Brooks said Republicans and Democrats will likely ignore Buchanan if he is the Reform nominee until he proves he is gaining significant support. Various polls have shown Buchanan receiving 5 to 9 percent of the vote.

"You focus on your real opponents, not your imagined opponents," Brooks said.

In his speech Monday, Buchanan also called for an end to affirmative action and said all Americans should learn English and a common history of American heroes.

"The backsliding toward hyphenated Americanism must end," he said.

Buchanan also appeared to call for school vouchers, which give parents funds to send their children to private or parochial schools. Jewish groups are split over the voucher issue.

"If I'm elected president, the bureaucrats at the Department of Education are not going to be testing kids, they're going to be testing the magic of the marketplace," he said.

When asked for his reaction to Buchanan's call to halt legal immigration, Leonard Glickman, executive vice president of the Hebrew Immigrant Aid Society, said it was "shortsighted" and failed to recognize the contributions immigrants can and have made to the country.

"This kind of nativism really has no place on our country's agenda," he said.