Washington — Following an embarrassing first effort, pro-nuclear-freeze forces are regrouping for an expected win this week in the House. They will almost certainly be better prepared this time.
''It wasn't as smoothly handled as it might have been,'' concedes Rep. Jim Leach (R) of Iowa, of the pre-Easter debate over an ''immediate, mutual, and verifiable'' freeze to the nuclear weapons race.
''The conservatives were much better prepared on the numbers,'' says a House leadership aide sympathetic to the freeze proposed by Rep. Edward J. Markey (D) of Massachusetts. The aide points out that during the March 16 debate, opponents turned the focus from the popular freeze notion to what they saw as the uncertain impact passing such a resolution would have on arms control efforts and on reducing the likelihood of nuclear war.
With the advocates in apparent disarray, final action on the issue was delayed until this week. In the meantime, supporters have been huddling to ''try to figure out what specifically the freeze does in specific cases,'' according to key freeze advocate Rep. Les Aspin (D) of Wisconsin.
When the issue comes up on Wednesday, supporters will have ready answers for technical questions, says Representative Leach, the chief GOP point man in the bipartisan freeze effort.
''I would acknowledge that there was a definitional problem'' on March 16, says Leach. This time supporters on the House floor will give definitions for such terms as ''weapons systems,'' he says, and make clear that the freeze is mutual, not the unilateral disarmament that opponents charge.
Supporters are also preparing to counter an expected series of weakening amendments that would make the resolution more acceptable to the White House and conservatives. In a letter to fellow GOP members, Leach admonishes that freeze advocates will oppose any amendment to ''needlessly dilute'' the resolution.
The change most feared by freeze advocates is proposed by Elliott H. Levitas (D) of Georgia which calls on a ''build-down'' pact with the Soviets. That plan would call for the two nations to agree that with each new weapon deployed, they would destroy two older weapons of equal potency. Such a proposal has already won considerable support in the Senate where the Markey freeze language is said to have little chance of passage.
Sources on both sides of the freeze issue expect the Markey language to face a long, tough debate on the House floor but to survive relatively intact.
''We think we've still got a chance at an alternative'' freeze resolution, says an aide for the Republican leadership, which is opposing the language, as proposed by Markey. But he adds, ''My instincts tell me it's (the Markey resolution) just got to pass.''
That prediction is based on the nationwide popularity of the freeze idea. Despite a White House media blitz to urge Americans to back Mr. Reagan's ambitious military buildup, Americans are still seen as siding with the freeze.
''Even though some of the advocates of the freeze may have some misgivings about the intent, they are still obligated to vote for it,'' says the GOP aide, who charges that the attitude is ''don't bother me with the facts'' because the concept is politically popular.
''I think the freeze resolution is a perfectly good approach to a very difficult and thorny problem,'' counters Representative Aspin. ''Congress can't negotiate an arms agreement with the Soviet Union. They can indicate the direction in which they think those negotiations should move.''
The Wisconsin Democrat points out that if the Soviets refuse to go along with the plan, the US defense buildup would proceed.