House Democrtatic leaders yesterday dropped the idea of a balanced 1982 budget but raised their ante for defense as they scrambled to outbid President Reagan for the support of conservative Democrats in the upcoming House budget battle.

After flirting for a day with a proposal to balance the 1982 budget by deferring any income tax cut for individuals until 1983, Democratic leaders decided to take their case to the House floor next week with only one sweetener: $6.5 billion more in spending authority for the Pentagon, enough to match Reagan's money for defense.

"It didn't buy us enough votes," said deputy Democratic whip Bill Alexander (D-Ark.), who had drafted the balanced-budget proposal in hopes that it, in conjunction with more defense money, would attract conservatives who hate deficits as much as they like defense. "So many southern conservatives are committed to the preseident that the value was negligible," Alexander added.

It had both "pluses and minuses," said House Budget Committee Chairman James R. Jones (D-Ola.), acknowledging the Democrats' dilemma of trying to keep liberals in line at the same time they try to win back straying conservatives.

The Congressional Black Caucus and another group of liberals led by Rep. David R. Obey (D-Wis.) are unhappy enough with the Democratic budget alternative drafted by Jones' committee that they fought successfully before the Rules Committee yesterday for the right to have separate votes on their proposals, which provide more money for domestic programs than either Reagan or the Democratic leadership would.

Ironically, in light of liberals' customary skepticism about the merits of balanced budgets, Obey's proposal would balance the budget by deferring personal tax cuts in the same was as the Alexander proposal that was rejected by the Democratic leadership.

Conservative Democrats were claiming 29 to 35 votes for a "bipartisan" version of the administration budget that Reagan has endorsed, and one Democratic leader said 31 Democratic votes for the Reagan-blessed budget now seem likely. Twenty-seven Democratic switches are needed for Reagan to win if the Republicans hold all their troops.

House Republican leaders say they foresee no more than three or four defections, but rumbles of dissatisfaction were heard yesterday from a dozen Northeast and Midwest Republican moderates who are said to be dissatisfied with both of the major alternatives. They want more money for mass transit, education, health and other domestic programs. Reagan has responded by inviting them downtown for consultations.

The republican dissension is matched or exceeded, however, by grumbles from Democratic ranks about the party leadership's handling of the budget. A high degree of testiness was reported to have marked a Democratic whip meeting that began a serie of strategy huddles yesterday.

Among rank-and-file, many members faulted Speaker Thomas P. (Tip) O'Neil Jr. (D-Mass.) for spending the congressional Easter recess abroad while Reagan was whipping up support for his budget and then virtually coneding defeat Monday as Democrats began thrashing around to pick up the pieces.

But the Democrats did rally in response to Reagan's invidious comparisons of his budget with the Democratic alternative in his televised address to a joint session of Congress Tuesday night. Both O'Neill and Majority Leader Jim Wright (D-Tex.) accused Regan -- in polite tones -- of erroneously claiming the Democrats would spend $141 billion more than he over the next three years, among other things.

They said he was using different sets of economic assumptions for the two proposals and that if the same assumptions were used for both, the Democrats will be spending less. The White House said Reagan stands by his assertions.

The $6.5 billion that the Democrats would add for defense would not affect actual spending for fiscal 1982 but rather would permit the Pentagon to obligate that much more for future years. This so-called budget authority figure would be $226.1 billion in both budget proposals.

For 1982 defense outlays, the Democrats are proposing $189.7 billion, compared to an administration proposal of $188.8 billion. Defense outlays for fiscal 1981 were budgeted by Congress at $162 billion.