LIBERALS HAVE always been good at internecine warfare; this fall's New York Senate race is a good example of how a head-on collision of two liberals may elect a conservative. The three-way race pits liberal Sen. Jacob K. Javits (R-NY) against slightly more liberal Democratic challenger Elizabeth Holtzman in a debilitating battle that may throw the election to an ultraconservative who opposes SALT, ERA ratification, and favors a constitutional amendment banning abortion.

The 76-year old Javits decided to remain in the race, running as a Liberal, even after he was soundly upset in the Republican primary by little-known Hempstead Town Supervisor Al D'Amato.

Although a September 30 New York Post poll shows Holtzman ahead of both Javits and D'Amato, the poll reflected widespread voter uncertainly that Javits, then in Washington, D.C., would run a full-fledged campaign. Now that he has emphatically stated his intention to do so, kicking off his New York campaign Tuesday, Javits makes Holtzman's early lead precarious. In 1970, a similar three-way race propelled Conservative James Buckley, as much a longshot as D'Amato appears today, into the Senate.

As his stunning victory over Javits indicates, D'Amato is not an opponent to be taken lightly. The product of a tightly run Republican county organization--the most effective in the state--that uses sophisticated new polling techniques along with oldtime political muscle in its foolproof effort to turn out the faithful, D'Amato has not yet lost an election.

Although organization is D'Amato's key asset, his rise is part of a larger demographic trend: the growth of suburbia. While Tammany Hall and other political machines traditionally were linked to the close, contentious atmosphere of the city neighborhood, D'Amato's power base is concentrated in the two sprawling counties, Nassau and Suffolk, that make up Long Island. Nassau County turns out more votes than any other county while Suffolk view with Manhattan for fourth place.

As presiding supervisor of Hempstead Town, D'Amato is chief of a huge patronage organization, To get a job as a lifeguard, a garbage collector, or a Long Island Railroad conductor in Nassau County one must be a registered Republican. A decade ago D'Amato was implicated in a scheme that required county employees to kickback 1 per cent of their salaries for the party. And just yesterday the Village Voice revealed that for years D'Amato's father had a no-show job on the Hampstead Town payroll.

Both Holtzman and Javits find D'Amato deeply offensive. Members of Javits' staff have called D'Amato a "political hack" and the Senator himself said that D'Amato was "temperamentally and intellectually unsuited to the Senate."

Yet by continuing his own campaign, Javits not only runs the risk of helping to elect D'Amato but he inadvertently may cause a statewide victory for Presidential candidate Ronald Reagan. Javits' presence on the Liberal line may draw enough votes to independent candidate John B. Anderson, also running as a Liberal, to cost Carter the election Anderson's campaign strategists in New York say they see Javits' candidacy as a "tremendous Boon" to the Anderson campaign.

Persisting in a campaign after a primary defeat is sometimes a sign of feisty independence or genuine dissatisfaction with the alternatives presented to the voters. But in Javits' case, it seems to be little more than the pique of an old man who does not want history to read that he was voted out of office. The New York voters were rude to their senior senator when they handed him a primary defeat on September 9, and he seems to be reciprocating in kind.

Javits undoubtedly has an outstanding record in the Senate; Ralph Nader's survey of congressional aides pinpointed the New Yorker as the Senate's brightest, and second most influential, member. The ranking minority member of the Foreign Relations Committee, Javits was responsible for shepherding the complicated 1973 War Powers Act through Congress.

And yet one could hardly hope for a better successor to Jacob Javits than Elizabeth Holtzman. Their styles match almost to a fault; both are characterized as extremely intellectual, hard-working and issue-oriented, if detached and aloof from their colleagues. And both have worked to champion social justice issues, both have remained committed to liberalism when it was no longer a popular cause.

And yet two days ago New York liberal witnessed a particularly distressing spectacle: Javits attacking Holtzman, who shares many of his positions on the issues, as an extremist saddled with all the "doctrinaire naivete of the left." By turning his wrath on the infinitely preferable Holtzman, the aging Senator has chosen a graceless--if not downright irascible--way to end his illustrious 24-year career. Javits' attacks only serve to give credence to D'Amato's charges that Holtzman is a "radical," by which D'Amato means a Communist sympathizer.

Javits should withdraw from the race. Despite his statements, he has demonstrated that he has neither the inclination, energy, or money to run a viable campaign. The fact that in the primary a distinguished incumbent Senator like Javits could not raise as much money as an unknown machine politician like D'Amato belies a certain, unbecoming complacency. (Javits raised $900,000, while D'Amato spent over a million.)

JAVIT'S PERSISTENCE in the race turns the classic liberal-consecutive confrontation between Holtzman and D'Amato into a confusing parlay of labels designed to obfuscate the issues. Javits tries to represent himself as the moderate between two extremists; D'Amato sees himself as moderate in contrast to two wild-eyes liberals; Holtzman calls herself the only "genuine" liberal.

In recent years Javits has become more and more isolated in the Republican Party. Although he disagrees violently with most of Ronald Reagan's positions, he was forced under New York rules to endorse Reagan in order to attend the Republican convention. With the rightwing in ascendence in the Republican Party, Javits' own native liberalism, the liberalism he is well known for, will become even more tightly constrained by circumstance.

Holtzman, in fact, may be better able to represents Javits' legacy than Javits himself.