OS ANGELES - Tom Hayden, the liberal activist and California state senator, arrived here yesterday to be a convention delegate for a Democratic Party he barely recognizes. Al Gore's running mate, Senator Joseph I. Lieberman of Connecticut, was picked for his centrist credentials. The Democratic platform, written weeks ago with scant public notice, is so moderate that much of it sounds Republican.
''If a dentist worked his way through the Democratic convention, he would find a lot of bitten-off tongues,'' Hayden said. But like most delegates, Hayden is willing to put aside his differences to help elect the Gore-Lieberman ticket. The potential election of Republican George W. Bush ''is a big motivator,'' Hayden said.
Still, disputes are simmering just below the surface. The AFL-CIO has worked against Gore and Lieberman in trying to defeat free-trade deals, but the union has endorsed the Democratic ticket. Many union members, who make up 28 percent of the delegates, remain unhappy with the party's strong tilt toward free trade and especially the US role in the World Trade Organization.
Similarly, the teachers' unions initially expressed some concern about the selection of Lieberman, who has voted for allowing a pilot project that would use public funds to help parents pay for private schools in Washington, D.C. Lieberman has since said that he would follow Gore's lead and oppose a national voucher program.
In addition, some delegates may not particularly care about the ''fiscal responsibility'' section of the platform, which for the first time says Democrats will pay off the public debt and will always balance the budget. The platform also supports the death penalty.
The disagreements are not merely from random delegates. House minority leader Richard A. Gephardt of Missouri and House minority whip David E. Bonior of Michigan disagree with Gore and Lieberman on free trade, but both have made clear in recent days that they won't focus on the dispute. Bonior said yesterday on CNN that he is convinced that Gore will be better on free trade than President Clinton.
Party chairman Joe Andrew promises that dissenters will be given a prominent speaking role.
''This is a real convention,'' Andrew said in an interview yesterday, referring to what he described as an artificially scripted GOP gathering two weeks ago in Philadelphia. ''We have nothing to hide.'' Andrew said he has ''no idea'' what some speakers will say.
But Andrew predicts that few delegates will complain publicly about the differences. Like the Republicans, the Democrats are willing to put aside their differences and put forward a unified message during a week that could make or break Gore's candidacy.
A sign of how the party intends to mold the message of the convention can be found in the platform. Unlike the Republicans, who held their platform hearings in Philadelphia amid considerable media attention right before their convention, the Democrats held their hearings in Cleveland weeks ago in sessions that received hardly any coverage or public notice. The process was strictly overseen by the Gore campaign, which wanted a mostly centrist document - and got it.
Much of the platform sounds as if it was written by the GOP, with calls for paying off the debt and supporting free trade. An effort by a group calling itself the Progressive Caucus, which included Hayden, tried and failed to insert a statement saying the United States should withdraw from the World Trade Organization.
US Representative Barney Frank, the Newton Democrat, said yesterday that most delegates probably disagree with the platform's support of free trade and the death penalty.
Nonetheless, Frank said, ''there is no real fight going on. There is a disagreement. What people are forgetting is that the conventions aren't the decision makers. The primaries have replaced the convention as the decision maker.''
And Gore easily won the primaries, defeating former senator Bill Bradley. An Associated Press survey found that 86 percent of the delegates favor Gore, while 8 percent back Bradley.
While Democrats are convinced that the platform appeals to the typical American, there is a risk that some union members and others would be attracted to alternative party candidates such as Green Party nominee Ralph Nader and whoever is determined to be the Reform Party nominee, Patrick J. Buchanan or John Hagelin.
Nader presents the biggest danger. He is at 4 percent in some national polls but has been in the high single digits in some California polls.
If Nader continues to remain that strong, he could siphon enough votes to cost Gore this vital state and the November election.
Democrats watched how Republicans sought to present themselves as a diverse party, with many minorities given prominent speaking roles. Andrew, the Democratic Party chairman, said this convention ''will be the most diverse in the history of the world.'' While that is impossible to prove, the AP survey found that the delegates here are more representative of the United States than at the GOP gathering. Eighteen percent of the Democratic delegates are black, compared with 4 percent at the Republican convention and 13 percent of the general population.
The AP survey also found that 68 percent of the delegates think gun-control laws are not strong enough; that 82 percent think guns should come with trigger locks; and that 52 percent think states should provide civil and other benefits for same-sex couples.
Asked for their top issue priorities, 30 percent said health care; 29 percent said education, and only 0.3 percent said moral values.
