SEATTLE, JULY 12 -- They cheered at the Young Republicans' national convention here whenever any speaker mentioned the Nicaraguan contras. They cheered the names of Robert H. Bork and Jeane Kirkpatrick. They cheered at every mention of Ronald Reagan, Nancy Reagan and even Maureen Reagan.

But the biggest, loudest cheers of all -- cheers, chants and waves of applause that echoed off the mirrored ceiling and brightly bedecked walls of the huge hotel ballroom here -- came whenever any of the featured speakers mentioned the name of the hero of the hour: Marine Lt. Col. Oliver L. North.

The six contenders for the 1988 Republican presidential nomination who traveled here this weekend to address 700 Young Republican leaders from around the country quickly discovered that the biggest applause line they could utter was any one containing a reference to North.

The overflowing support for North here reflected partly the "Olliemania" sweeping the country. But some Young Republicans said it also reflected a desire to find a single champion everyone could support. And one clear message of this gathering was that none of the Republican presidential contenders has anything like uniform support among the party's youthful activists.

In 1980, younger Republicans rallied in large numbers around Ronald Reagan. This time, though, the group is split every which way, with no candidate yet able to claim firm or broad support among the young people who do much of the grunt work in political campaigns.

"In one sense we like all the candidates, and in another there's not anybody that we really like," said Jason Miko, a thoughtful senior at the University of Arizona.

Miko said he came to the convention mildly inclined to support retired general Alexander M. Haig Jr. for president. After listening to two days of candidates' speeches he described himself as leaning toward Rep. Jack Kemp (N.Y.).

Then there was Duane Smith Jr., a Chattanooga, Tenn., businessman. He said he was for "{Vice President} Bush and {Sen. Robert J.} Dole {Kan.}, in that order," before he came to Seattle. By the end of the weekend he was for "Dole and Bush, in that order," but he said he was also "very seriously impressed with what I heard from Gen. Haig."

Of the six presidential contenders who addressed this convention, five -- Bush, Dole, Haig, Kemp and former senator Paul Laxalt of Nevada -- were warmly received.

In contrast, Marion G. (Pat) Robertson, the television evangelist, received cold, almost rude treatment. Except when he mentioned North, setting off the ritual cheers, Robertson watched members of the audience reading newspapers and carrying on noisy conversations in their seats throughout his speech.

That reception may indicate how difficult it will be for Robertson to bridge the divide between his fervent evangelical supporters and the more traditional breed of party worker represented here.

Most of the candidates gave similar speeches, hitting on the contra war in Nicaragua, the Strategic Defense Initiative, the budget deficit and the nomination of U.S. Appeals Court Judge Bork to the Supreme Court.

The one hopeful who forged a different rhetorical path was Dole. He focused his remarks on the necessity for Republicans to show "compassion" and "sensitivity" toward poor, homeless and unemployed Americans.

"When I look out on a Republican gathering," Dole went on, "I should see 100 black faces. I should see 50 wheelchairs." In fact, he saw a half dozen of the former and none of the latter among the neatly tailored delegates seated before him.

On a before-and-after scale -- that is, which candidate won more applause after his speech than before -- Kemp was the clear winner, with Dole in second place. Bush received a loud reception when he was introduced and a slightly softer one when he finished. Haig and Laxalt received equally restrained applause before and after, while Robertson was received coldly.

If the assembled young Republicans seemed unsure which Republican candidate would be their champion, they also seemed unable to decide which of the Democratic contenders is their favorite villain. None of the Democratic names drew much response from this crowd; the one whose name invariably moved the audience to boos and hisses was Sen. Edward M. Kennedy (Mass.), who is not running for president.

In addition to the parade of presidential candidates, the convention also had to pick new leadership for the Young Republican National Federation, which claims to represent 200,000 party workers between the ages of 18 and 35.

The election for chairman came down to choosing between a conservative and a moderate. Abortion emerged as the central substantive issue, and the strong right-to-life side lost. The moderate candidate, Richard Jacobs of Jackson, Tenn., won an easy victory despite his refusal to endorse the antiabortion plank in the Republican Party's 1984 platform.