George Bush ducked an awkward punch from Alexander Haig on his role in the Iran-contra affair.

Bob Dole dodged and straddled the obvious divisions within the Republican Party on the nuclear arms agreement President Reagan is about to sign with Soviet leader Mikhail Gorbachev.

And while those two "heavyweights" of the Republican presidential field were preoccupied with their own problems, several of the much-derided Democratic "dwarfs" performed impressively in the first network television debate of the 1988 campaign.

Last night's two-hour, prime-time NBC program, with alternating sets of Democratic and Republican aspirants taking cues and questions from moderator Tom Brokaw and each other, largely debunked the notion that there is a huge "stature gap" between the rival fields.

The youngest man on the Kennedy Center stage, 39-year-old Sen. Albert Gore Jr. (D-Tenn.), showed presence and toughness, scrapping effectively with rivals who lead him in the national polls.

Gore's impressive network TV debut to a national audience was almost matched by Massachusetts Gov. Michael S. Dukakis (D). Allowed to go almost unchallenged by his rivals, Dukakis efficiently carried out his chosen role as one Democrat who is primed to take on the Republican record in both domestic and foreign policy.

Jesse L. Jackson, the leader in the Democratic polls, also had a good night, mixing humor and passion as he asserted a claim to superior experience in foreign policy, firmness in defending America's interests and compassion for the needy at home.

Jackson was not the only preacher to score points. The Republicans' clergyman, Marion G. (Pat) Robertson, once again showed his mastery of the television medium that has been his church and his business for many years. No one said anything mean about Robertson, whose evangelical following is coveted by rivals who figure the lawyer-preacher's high poll negatives will eventually catch up with him. Left alone, Robertson stroked conservative sensibilities in his most reasonable and engaging manner.

Robertson's success was bad news particularly for Rep. Jack Kemp (R-N.Y.), who has seen the minister make a run at his right-wing base. Kemp had a rough night, often leaving his questions and answers unfinished as time ran out, and once being admonished to stop talking by Brokaw and Dole.

Former Delaware governor Pierre S. (Pete) du Pont IV, another of the trailing GOP contenders, held his ground more effectively than in the October Public Broadcasting System debate that marked the Republicans' joint TV debut. As in that debate, former secretary of state Haig rolled grenades at Vice President Bush and other targets and saw some come flying back at him.

On the Democratic side, chief target of the night was Sen. Paul Simon (Ill.), who was pressed repeatedly to explain how he would finance his many domestic spending proposals while balancing the budget in three years. Simon asserted it could be done, but never quite said how.

Rep. Richard A. Gephardt (D-Mo.), whose hopes of an opening-round victory in the Feb. 8 Iowa caucuses have been severely endangered by Simon's surge to the front in that state, led the assault, charging "Simonomics" was as illusory as "Reaganomics" had been.

But Gephardt came under withering cross fire from Gore, who questioned the congressman's support of the 1981 Reagan tax cuts. Gephardt was left spluttering on the screen that such criticism of him, a "leader," was unbecoming for a "backbencher" like Gore.

Former Arizona governor Bruce Babbitt (D) accused the others of fiscal "flim-flam." To dramatize his point for the viewers, he challenged any of his rivals to "stand up" and admit, as Babbitt has done, that higher taxes would be part of any solution to the budget deficits.

Except for a reluctant Gephardt, who advocates an oil-import fee, they all declined Babbitt's invitation. The Arizonan smiled triumphantly, but at other points cameras showed him -- like Simon -- frowning uncomfortably at the proceedings.

The other person who plainly did not appear to be enjoying the evening was Senate Minority Leader Dole (R-Kan.), whose handlers had promised a more animated and challenging performance than he turned in on the PBS debate. While Bush diligently -- if not deftly -- defended the intermediate-range nuclear forces (INF) agreement against criticism from Haig, Kemp, du Pont and Robertson, Dole dithered. Finding fault with all the Democrats who had rushed to embrace Reagan's prize diplomatic handiwork, Dole said grumpily, "I've never let the president down yet . . . but we ought to look at it, study it."

What Dole is really studying is how he can hold a share of the Republican conservative vote skeptical of any dealings with the Soviets while still embracing a treaty the polls show most voters -- including Republicans -- strongly support.

Wooing the right wing while proclaiming himself a better bet than Bush to win independent and Democratic votes in the general election puts Dole constantly under pressure. He also waffled last night on whether the leading figures in the Iran-contra affair deserved pardons and -- with minimal regard for consistency -- endorsed both the minority and majority reports of the congressional committees that investigated that scandal.

Bush's most awkward moment came when -- with little disguise -- he simply refused to answer Haig's challenging question on the advice Bush gave Reagan on selling arms to Iran. Rather than break his self-protective code of silence, Bush filibustered. For the rest of the evening, he deflected criticism from other flanks, but he never got off a single retaliatory shot as effective as the one he landed on du Pont in the earlier debate.

Bush tried to cast himself as the chief Republican critic of the Democratic sextet. But the man who really played that kind of preemptive general election strategy well was Dukakis, who said he would "love" to make the Democratic case against Bush and the GOP. Dukakis' small but forceful gestures and his serious tone and expression play better on television (a familiar medium for him) than in the hall.

Gore has greater physical stature and larger lungs, and at times has overpowered the cameras, but last night he was always in control, making his points concisely and clearly.

The two House members, Kemp and Gephardt, had been in slumps coming into the debate and neither did much to revive himself. The New York Republican and the Missouri Democrat cast themselves as reincarnations of President John F. Kennedy. But neither was able to maintain the cool aplomb Kennedy showed in his 1960 debates with Richard M. Nixon, and neither had a speck of his humor.

The candidate of passion and humor was Jackson, whose lead in the race is a source of dismay to many of his party's leaders. Many Republican officials feel just as nervous about Robertson, and for those party leaders, the strong performance of the two preachers made last night's proceedings an ambivalent sendoff to the election year.