One discreet White House job feeler to Sen. Jacob K. Javits got nowhere, but President Carter is being urged to keep trying, in view of what is at stake: the presidential election itself.

The fear in the Carter camp is that Javits, old and ailing, could in the twilight of a distinguished political career prove the instrument of Carter's defeat. Javits, though upset for Republican renomination in the Sept. 9 primary, is running on the Liberal ticket. That could strengthen the Liberal Party's presidential nominee, Rep. John Anderson, sufficiently to let Ronald Reagan defeat Carter in New York.

Contrary to the brabado displayed by Carter campaign manager Hamilton Jordan on his most recent political mission here, the president simply cannot be reelected without New York's 41 electoral votes. Although Jordan told New Yorkers his chief could do without thier troublesome state, the hard reality is that Ronald Reagan will have been elected president without anybody's staying up for late returns if New York goes Republican.

Secret poll results from New York consequently make unpleasant reading at the White House. Carter and Reagan are in a virtual dead heat, with two unpleasant details from the president's standpoint: first, although Reagan has yet to win over the state's normal Republican vote, he may well do so; second, the big, habitually Democratic Jewish vote is simply not coming around to Carter.

Under these circumstances, New York's Liberal Party -- which had been lingering through a slow death of attrition until it became a shelter for the noncollaborating Anderson and Javits -- could do in Carter. "I'm afraid Javits and Anderson on the same ticket could bring support to each other without endorsing each other," a Carter strategist told us.

Jack English, the New York Kennedy Democrat who since the national convention has been Carter's deputy national campaign chairman, had this in mind on the evening of Sept. 9 when he heard the shocking news that the state's increasingly conservative Republican electorate had rejected Javits. English urged the president to place a condolence telephone call to the liberal Republican.

Carter did so. Nothing so crude as a job offer was made in return for Javits' bowing out of the race. But the promise of a high-level diplomatic post was conveyed from an authoritative Carter operative to a Javits confidant. It aroused no interest, and Javits is now on the state ballot to stay.

The establishment Republicans who have been Javits' closest supporters told him that it would be "ignominious" to close out his political career by quitting the Senate race in return for an ambassadorial post. It is indeed ignominious for Javits, at age 76 in his 24th year in the Senate, to finish as a pawn in presidential politics.

It is also demanding for Javits, once considered New York's premeir vote-getter, to find himself running third to two unknowns, ultra-liberal Democratic Rep. Elizabeth Holtzman and Javits Republican conqueror, ultra-conservative township supervisor Alfonse D'Amato of Hempstead, Long Island. Carter strategists hope that Javits might end his campaign if convinced he would split the Liberal vote and thereby elect D'Amato, a man whose style and philosophy offend him.

But two separate polls show Holtzman, her fantastic opposition to all defense spending bills either unknown to or uninteresting to New Yorkers, nearly 20 percentage points ahead of D'Amato and Javits. The Javits candidacy, therefore, is more of a threat to Carter than to Holtzman.

Javits' told friends in organized labor, panicky at the idea of Ronald Reagan in the White House, want Javits to erase that threat by deactivating his campaign. AFL-CIO President Lane Kirkland is particularly anxious that some arrangement be found for Javits to conclude his days as a senior diplomat in return for quietly helping keep labor's enemy from being elected president.

Javits, nomially at least, still suports Reagan instead of fellow Liberal Anderson. He may feel no debt to labor leaders, who (with the notable exception of teachers' union cheif Al Shanker) quickly abondoned Javits once he had lost the Republican primary.

That confronts Jimmy Carter with a peculiar task in the state his campaign manager two weeks ago dismissed as non-essential. His worried advisers here want him to go on bended knee to ask lifelong Republican Jack Javits, entering his final political hours, to help him keep a Republican out of the White House.