DES MOINES, IOWA -- Gov. Michael Dukakis and Rep. Richard Gephardt ducked a bare-knuckled brawl for the soul of the Democratic Party last weekend, settling instead for gloves-on combat over who is more electable.

Both pulled back during their ballyhooed one-on-one debate here. Gephardt dulled his previous portrait of the Massachusetts governor as a regional candidate who imitates Ronald Reagan's trade policy. Dukakis seized the offensive by slashing the congressman's past conservative positions on taxes and defense, but edged closer to Gephardt-style protectionism on trade and farm policies.

Peace between Dick and the Duke is not at hand. That was shown during the debate by Bill Carrick, Gephardt's national campaign manager, when Dukakis asked about his opponent's pro-defense votes. Gephardt hastily retreated from that record. But South Carolinian Carrick nudged a colleague and said he couldn't wait to get Dukakis in the Super Tuesday South to challenge him on defense. Tactical advantage, not ideological conviction, is at stake.

Iowa is no two-man race, but a closely bunched field with no clear leader. Although Sen. Paul Simon's unwashed liberalism excites left-wing activists, thirst for victory is so intense that no ideologue is likely to win the February caucuses. That explains interest in Dukakis and Gephardt and tells why their collision was muted.

While Gephardt's strategists were delighted to get Dukakis into a confrontation seen live by New Hampshire primary voters over Boston television, they were concerned about disturbing the unity of a party still scarred by the bloody strife of the '60s and '70s. Gephardt pulled his punches, limiting to his opening statement suggestions that the ''Massachusetts Miracle'' is no economic model for America and that Dukakis does sound ''a lot like'' President Reagan on trade.

Nor was Gephardt the feisty fighter he was here last month debating Republican presidential hopeful Jack Kemp. He let Dukakis take and hold the offensive with attacks on his votes in Congress (for tax cuts and weapons systems) and an assault on his oil import tax. By careful design, the governor steered the debate so it compared an executive decision maker (himself) with a legislative trimmer (Gephardt).

But Dukakis also pulled back. In Houston July 1 at the seven-candidate debate, he flourished his party's free-trade heritage against Gephardt's protectionism. But here he reduced their dispute to a technical argument that the president can -- and should -- retaliate against Japan, but without needing a Gephardt amendment to augment his powers.

In fact, Dukakis seems genuinely dismayed by a Hobbesian world of retaliation, embargoes and trade wars. But the electability issue compelled him toward the Harkin-Gephardt farm bill, which would build a protectionist wall around artificially high U.S. farm prices.

A few days before the debate, Iowa's Sen. Tom Harkin -- neutral for president -- advised Dukakis. Although only 45 percent of Iowa's farmers support Harkin-Gephardt, he said, that 45 percent will attend Democratic caucuses and the others won't. So when Gephardt asked whether he would vote for the bill, Dukakis fudged: ''I don't think that I'd do it right now.''

As in Houston, Gephardt reserved his harshest words about Dukakis for newsmen after the debate was over. Without State Democratic Chairman Bonnie Campbell around to witness breaches of party peace, he said of Dukakis: ''Now we know what he's against, but what's he for?''

Gephardt also told postdebate interviewers a ''candidate for unilateral disarmament'' cannot carry the South -- presaging his swing through Super Tuesday Dixie next week. But on stage with Dukakis, he recanted his pro-defense votes (many cast before his leftward shift in preparing for the presidential campaign).

This surely does not replicate 1972 bloodletting between George McGovern and Hubert Humphrey over the party's course in national security and foreign policy. Gephardt and Dukakis, along with their rivals, must purvey their party's McGovernesque consensus. Thus, when we asked them separately after the debate whether permanent communist rule in Nicaragua would be acceptable, we heard remarkably similar language equating the Sandinistas with Chile's dictatorship.

The Duke and Dick, plus four other candidates who hit Iowa's highways last weekend, told Democrats what the consensus requires. Each projected himself as the nominee best able to carry Iowa, for the first time since 1964. Neither examined whether Democratic policies have caused that 20-year failure.