WASHINGTON — A Republican primary challenge to Senator Chafee of Rhode Island is attracting backing from national groups that favor tax cuts and a strong U.S.–Israel relationship.

The mayor of Cranston, R.I., Stephen Laffey, 43, is hoping to unseat Lincoln Chafee,a Republican who was appointed to the Senate in 1999 after the unexpected death of his father, John Chafee, and who won election to his father’s former seat the following year.

The main fund-raising arm for Senate candidates, the National Republican Senatorial Committee, is coming to Mr. Chafee’s defense. About 11 months before the September 12 primary, the committee launched a series of television ads attacking Mr. Laffey’s record on taxes and tarring him as a “slick” ally of the oil industry.The latter charge is taken as a slur by many environmentally conscious Rhode Islanders.

Mr. Chafee, 52, has made enemies of some political activists,though,with his votes against President Bush’s tax cuts, against the Iraq war, and against a law authorizing sanctions on Syria. In 2004, the senator flirted with leaving the Republican Party and pointedly declined to vote for President Bush. Mr. Chafee told the Providence Journal that he wrote in the name of President George H.W. Bush as a “symbolic protest.”

Those moves have produced support for Mr. Laffey.

“We’ve certainly hit a nerve,” Mr. Laffey said of the intervention in the race by the National Republican Senatorial Committee. “They obviously are very, very nervous.”

A political group that advocates supply-side economics, the Club for Growth, has come to the defense of Mr. Laffey, who is running on a platform that calls for reining in the surge in federal spending.The club,which is known for targeting Republicans like Mr. Chafee who have questioned the wisdom of tax cuts, formally endorsed the Cranston mayor last month and is expected to direct a generous flow of donations towards his campaign.

Some in the pro-Israel community are also entering the fray on Mr. Laffey’s behalf, while others are hanging back. The Washington Political Action Committee, which donates to American candidates who support Israel, recently gave Mr. Laffey the maximum $5,000 contribution, according the group’s founder, Morris Amitay. He said the donation was prompted primarily by serious concerns about Mr. Chafee’s position toward Israel.

“We’d like to see the young Chafee retired from the Senate,” Mr. Amitay said. “He has one of the worst records of anyone in the Senate, definitely in the bottom 10% of class as far as pro-Israel initiatives are concerned.”

The contest may be shaping up as a reprise of sorts of the 1988 Senate race between Mr. Chafee’s father and the Democratic nominee, Richard Licht. That year, pro-Israel groups enthusiastically supported Mr. Licht, who is Jewish and was twice elected as lieutenant governor of Rhode Island. The heated 1988 contest also spawned allegations that the American Israel Public Affairs Committee, which has a policy of not supporting or opposing candidates, was covertly promoting Mr. Licht’s campaign. The organization acknowledged that a junior staffer engaged in an unauthorized attempt to generate positive press coverage for the challenger.

Ultimately, John Chafee won 55% of the vote, handily defeating Mr. Licht, who garnered 45%.

Mr. Amitay said Mr. Laffey has an “excellent shot” at ousting Mr. Chafee in the primary, but if that fails, the Washington PAC will back the Democratic nominee in the general election. Democrats vying for the nomination include the Rhode Island attorney general, Sheldon Whitehouse; the secretary of state, Matthew Brown, and a former marine captain running on an anti-war platform, Carl Sheeler.

Mr. Amitay denied that the animus toward Mr. Chafee stems from the 1988 race. “Lincoln Chafee in his own right can be considered not to be a friend of Israel,” Mr. Amitay said. “We’re not visiting the sins of the father unto the son here.”

Mr. Chafee’s campaign manager, Ian Lang, rejected the notion that the senator has been unfriendly towards Israel. “Senator Chafee is committed to the long-term security and survival of Israel,” Mr. Lang said, noting that his boss supported President Bush’s “road map” for peace and its promise of a two-state solution to the conflict between Israel and the Palestinian Arabs. “He believes that’s the only way you can have peace in the Middle East.”

Mr. Lang also said Mr. Chafee recognizes that Israel faces “very real threats.”

Perhaps no other act by Mr. Chafee has angered the pro-Israel lobby more than his 2003 vote against a measure aimed at reining in the regime in Syria, which is on the American government’s list of state sponsors of terrorism. The Rhode Island Republican was one of only four senators to vote against the Syria Accountability Act. “The symbol of the United States as cracking down on an Arab nation ultimately harms our interests in many very important parts of the world,” Mr. Chafee warned on the Senate floor.

For his part, Mr. Laffey is playing up his pro-Israel views. “I don’t think you’re going to find a candidate has a stronger opinion on respecting Israel,” he said.”It’s their country.They built it. They get to stay.”

Mr. Laffey, an investment banker who grew up in Cranston but spent most of his career at a financial firm in Tennessee, said he expects the central issue in the campaign to be the fiscal mismanagement of the federal government.”I just think Washington’s one gigantic mess,” the candidate said. “There are not enough people, including Mr. Chafee, willing to stand up to special interests and do what’s right for the country.”

It’s this kind of talk from Mr. Laffey that attracted the Club for Growth. “He’s committed to limited government, lower taxes, including a supply side approach,” the club’s president, Patrick Toomey, said. “He’s really our kind of guy.”

Still, Mr. Laffey does not hew entirely to the club’s small-government agenda. He has endorsed raising federal fuel efficiency standards for cars, a move which he hopes will help wean America from foreign oil. “This is a national defense issue,” the challenger said. “When I see oil at $10 a barrel, I know Iran and Saudi Arabia will be focusing on their own problems.”

After taking office as mayor of Cranston, Mr. Laffey raised taxes to help dig the city out of a massive financial crisis. Mr. Toomey said his group looked “very, very carefully” at the issue and determined that the tax hike was the only way for the city to avoid default on its bond obligations. “We’re convinced that he really had no choice,” Mr.Toomey said.

Asked about the claims that Mr. Chafee contributed to spiraling federal spending, Mr. Lang said, “That’s ludicrous.” Mr. Lang said the senator voted against the farm bill and the Medicare prescription drug plan, and has twice been recognized by an anti-deficit group, the Concord Coalition, for his commitment to fiscal prudence. “He’s probably the leading proponent of fiscal discipline in the senate,” the campaign manager said.

Mr. Lang noted that despite Mr. Chafee’s record of repeated snubs to the administration, he enjoys the backing of the Congressional leadership as well as Mr. Bush.

In 2001, Mr. Chafee was the only Republican senator to vote against giving the current president the authority to take military action in Iraq.

Asked why Mr. Bush and his allies are backing someone who has not been loyal to the GOP, Mr. Lang said, “They want this seat to remain Republican.”

Mr.Lang said polls show that Mr.Laffey would be defeated by any of the Democratic candidates, costing the GOP the seat and possibly control of the Senate if there are other Republican losses. “To be a Republican and win in Rhode Island is an accomplishment,” Mr. Lang said.

Mr. Laffey offers some criticism of Mr. Bush on budget issues, but the challenger’s rhetoric is largely devoid of complaints that Mr. Chafee has been disloyal to his party and his president. That approach may be driven by the fact that registered Republicans could wind up a minority of those who vote in Rhode Island’s Republican primary. At last count, the state was home to about 72,000 Republicans, but nearly 340,000 voters who are not enrolled in any political party and, under the state’s open primary rules, could choose to vote in the Chafee-Laffey race.

Mr. Laffey’s anti-abortion position could give him a boost in a state with a sizable number of Catholic voters,but he is downplaying that issue. “I’m not running on a social conservative background.I’m running because we have a financial disaster in Washington,” he said.