In this first year in Congress, Jerome A. Ambro (D-N.Y.) voted for common site picketing and against various costly defense projects and agreed 89 per cent of the time with the leftist Americans for Democratic Action. Clearly a "liberal."

But wait in his second year in Congress, Ambro voted to limit state antitrust suits and to ban school busing for integration, and ended up with an ADA rating of 50 per cent. Maybe a "moderate?"

Wait again. This year, his third in Congress, the Democrat from Long Island voted against funding the B-1 bomber, but in favor of the A-10 attack jet. He voted against federally funded abortions, but in favor of federally funded "gay rights" lawsuits.

Is this man "liberal?" "Conservative?" "Moderate?"

"For Ambro, as for scores of other junior members of Congress, the answer to that question is apparently "none of the above."

In an institution as individualistic as the 95th Congress, it is difficult to find anyone who epitomizes the group. But Ambro's unpredictable, nonideological voting record seems typical of a large segment of House members who do not seem to follow any of the traditional voting patterns these days.

"There's still a hard core," the jaunty Ambro says, "a hard core on both sides that votes a particular philosophy. But the great numbers in the House right now are guys who don't want to be categorized. I don't want its that's sure.

Why? Politics is a major reason, Ambro says frankly.

"I'm a Democrat representing two counties that gave President Nixon the biggest pluralities he ever got. It's . . . counterproductive to be tagged a 'liberal' and then go into some conservative town to campaign."

Accordingly, Ambro, a 49-year-old who came to the House after holding various local offices in his suburban district, keeps an ear closely attuned to his constituents in deciding how to vote on each bill.

"I take each vote as it comes," he says. "My first thought is, 'Does this have anything to do with Long Island?' If it does, I want to vote for my district."

Ambro maintains that the decline of ideological voting patterns leads to sounder decision-making in Congress. "You're getting guys really examining the issues," he says, "instead of voting knee-jerk."

But he admits that the lack of a strong personal philosophy and the heightened concern about constituent's reactions to each vote leads to "gutless" choices on controversial subjects.

His prime example is an amendment introduced by Rep. Lawrence P. McDonald (D-Ga.) to prohibit federal legal aid lawyers from bringing "gay rights" suits. When McDonald proposed the prohibition, members laughed aloud and voted it down on a voice vote. But when McDonald demanded a recorded tally, a strong majority sided with McDonald.

"That was gutless," Ambro says. "It was just the code word in there - 'gay'. A lot of people who thought McDonald was dippy were afraid to vote against him.

"It's a real problem - code words sway a lot of votes around here now."

Ambro, who prides himself on his bad relations with his party's leadership, says another consequence of the decline of ideology is the disappearance of party discipline among House Democrats.

"We are an independent group," he says proudly. "There's no such thing as party discipline among first, second, third-term people here."

That "revolution," according to Ambro, is a key reason for President Carter's problems with the heavily Democratic Congress.

"The White House guys with four leaders in a back room control the Congress," he says. "The White House thinks a congressman will vote its way because he sees [Majority Whip John] Brademas going thumbs up or thumbs down when he comes onto the floor.

"I wonder how long before this Congress can disabuse the White House of that notion.?"