As the battle for control of Congress grinds into its final two weeks, Republicans are following the ideological script of one of their most aggressive and least visible political strategists.

Since he began working for Jesse Helms a quarter of a century ago, Arthur J. Finkelstein has helped elect conservative Republicans with a two-fisted style that pummels Democratic candidates as denizens of the far left. This year, with millions of dollars channeled through the National Republican Senatorial Committee, Finkelstein has emerged as a major force in a slew of high-profile Senate races.

His style is unmistakable -- an avalanche of attack ads painting Democrats as "liberal," "ultraliberal," "embarrassingly liberal" and "unbelievably liberal."

"Essentially he has dictated the message strategy for the Republican Party," said Democratic consultant Mandy Grunwald, who is helping Minnesota Sen. Paul D. Wellstone fend off Finkelstein's effort to put him in a "Liberal Hall of Fame." "I don't know a Senate race in the country where the Republican message isn't charging liberal, liberal, liberal."

If his longtime friend and patron, Sen. Alfonse M. D'Amato (R-N.Y.), had his way, Finkelstein would also be running Robert J. Dole's presidential campaign. According to Bob Woodward's book "The Choice," D'Amato threatened to withhold his endorsement of Dole unless the Kansan hired Finkelstein as his chief strategist. (Finkelstein declined a lesser post, and D'Amato backed Dole anyway.) Since D'Amato brought him in as a senior consultant to the Republican Senate campaign committee, which he heads, Finkelstein has been paid $500,000 to put his stamp on this year's elections. Separately, at least three GOP candidates have dropped their longtime consultants to hire Finkelstein. Some Republicans say D'Amato, who controls a $10 million budget for advocacy advertising, has pressed others to do the same. Said one GOP consultant who has competed with Finkelstein: "D'Amato leaned on every U.S. Senate candidate out there just like he leaned on Dole: Get rid of everyone, just hire Arthur.' D'Amato has turned on the financial faucets for those who hired Arthur, just massive expenditures." D'Amato said that was "absolutely not" true. "If anybody comes to me, I would tell them, I don't think there's anybody better," he said. D'Amato said he had recommended Finkelstein only to South Dakota Sen. Larry Pressler, who "sought out my advice." Finkelstein, said D'Amato, "is incisive. He's courageous. He tells you what the situation really looks like. . . . He's one of the most honorable, decent people I've ever met. His political skills are second to none." Some of Finkelstein's past and current clients -- including Sens. Helms (R-N.C.), Lauch Faircloth (R-N.C.), Don Nickles (R-Okla.) and Robert C. Smith (R-N.H.) -- are outspoken opponents of gays. In 1990, while Finkelstein was overseeing his strategy, Helms ran ads accusing "homosexuals" of "buying this election for Harvey Gantt," his Democratic opponent, because Gantt "will support their demand for mandatory gay rights." Smith opposes allowing gays to adopt children. Nickles sponsored the Defense of Marriage Act, aimed at preventing same-sex marriages. Finkelstein's role with these senators became a public controversy last month when Boston magazine reported that the 51-year-old consultant is gay and living with a male companion and two adopted children on Massachusetts's North Shore. The magazine accused Finkelstein of hypocrisy, as did New York Times columnist Frank Rich, who said Finkelstein "sells his talents to lawmakers who would outlaw his family's very existence." Finkelstein's office responded with a terse statement: "I am disappointed some would stoop to this level. I keep my private life separate from my business life -- something my friends and clients understand, appreciate and respect." Finkelstein told the New York Post that "all my friends and family know I'm gay." D'Amato, a gay rights supporter, told a Washington Post reporter last month that he knew of Finkelstein's sexual orientation and that it has "nothing to do with his ability" to serve political clients. Another Finkelstein secret, until it was revealed by a Jerusalem newspaper, is that he helped Binyamin Netanyahu win election as Israel's prime minister. Television ads suggested by Finkelstein linked images of bombed-out buses with pictures of then-Prime Minister Shimon Peres and Palestinian leader Yasser Arafat -- "a dangerous combination for Israel." A reclusive figure who almost never talks to reporters, Finkelstein did not respond to an interview request. The son of a Brooklyn cabdriver, Finkelstein lives in Ipswich, Mass., and keeps an office in Irvington, N.Y. He is working separately for such GOP Senate candidates as Minnesota's Rudy Boschwitz, Rhode Island state Treasurer Nancy Mayer, New Jersey Rep. Dick Zimmer, South Dakota's Pressler and New Hampshire's Smith. Finkelstein himself has been a minor issue in some of these races. A Minneapolis Star Tribune article referred to him as "the Terminator." Rep. Robert G. Torricelli, Zimmer's Democratic opponent, contends he is running not just against Zimmer but against Finkelstein as well. "The Republicans have bought his mantra," said Democratic pollster Mark Mellman, who is opposing Finkelstein in New Jersey and South Dakota. "He's a one-trick pony, and the trick is getting old. Slash-and-burn negatives is part of his style." The advertising Finkelstein has supervised has hammered at such traditional GOP themes as crime, taxes and welfare. In Rhode Island: "Liberal Jack Reed opposes the balanced budget amendment." In Minnesota: "Ultraliberal Paul Wellstone voted for the largest tax increase in American history." In New Jersey: "Tell liberal Bob Torricelli to stop raising your taxes." One GOP insider says that after winning the Senate committee contract, Finkelstein became the subject of backbiting "from other Republican consultants who viewed the Republican committees as a gravy train." D'Amato blamed the criticism on "envious people" and Finkelstein's status as "an individualist. He doesn't play the old-boy network. He doesn't wear a tie." "He makes James Carville look like Mary Poppins," said GOP consultant Mike Murphy, a former colleague. "He has contempt for a lot of the party establishment. He is brilliant, crazy and secluded." Murphy, Roger Stone, Dole media adviser Alex Castellanos and Dole pollster Tony Fabrizio are among the hard-charging consultants who once worked with Finkelstein and are sometimes called "Arthur's kids." Everyone understands Finkelstein's loyalty to his chief ally. During a recent meeting with a Senate candidate, one Republican said, Finkelstein took five calls from D'Amato in the space of several hours. Finkelstein's career has been dogged by controversy since he emerged in 1972 to help elect Helms in North Carolina. In 1978, while helping Carroll A. Campbell Jr. win a House seat in South Carolina, a Finkelstein poll raised questions about Democrat Max Heller, an Austrian-born Jew. According to the publication MetroWest Jewish News, the poll asked voters which "personal qualities" would make them more or less likely to support a candidate: "a Jewish immigrant" or "a native South Carolinian." It also raised the question of "U.S. aid to Israel." Both Finkelstein and Campbell have denied trying to make an issue of Heller's ethnicity. Finkelstein was a driving force at the National Conservative Political Action Committee, which used a barrage of negative ads in 1980 to help defeat such veteran Democratic senators as George McGovern, Birch Bayh and Frank Church. Finkelstein also mapped the strategy that enabled D'Amato, an obscure Long Island politician, to knock off then-Sen. Jacob Javits in a GOP primary, in part through tough ads that questioned Javits's failing health. By 1981 The Washington Post was writing about "the Finkelstein connection." His approach has remained remarkably constant. In 1988, Finkelstein helped Florida Sen. Connie Mack beat Democrat Buddy MacKay with an ad that shouted: "Hey Buddy, you're liberal!" In 1992, he guided D'Amato to reelection with spots calling the Democratic attorney general, Robert Abrams, "hopelessly liberal" and "too liberal for New York." Two years ago, Finkelstein helped a D'Amato protege, George E. Pataki, oust Mario M. Cuomo by tagging the New York governor "too liberal, too long."

Now the Republican Senate committee is trying to make the L-word stick in a torrent of advocacy ads, which D'Amato contends have been more than offset by Democratic and AFL-CIO spots. The question for Republicans is whether the Finkelstein approach can help them retain control of the Senate.

"He figures you just keep shooting the same bullets into someone," Grunwald said, "and eventually they'll fall over." CAPTION: Arthur Finkelstein's work was criticized recently as hypocritical because of his clients' anti-gay stands.