The campaign to limit state legislative terms in California -- though still well ahead in the polls -- may be suffering from a surfeit of friends in high places.

In the past month, Proposition 140, the more severe of the two separate term-limitation measures on Tuesday's ballot, has been endorsed by President Bush, Vice President Quayle and Sen. Pete Wilson (R-Calif.). During that same period, it has slipped five points in the polls, and now leads by 50 to 34 percent, according to a Los Angeles Times survey published last weekend.

Some proponents of term limitation believe the two developments are not unrelated.

"What drives this movement is anti-incumbent fervor, and I'm afraid that having promiment political leaders support it only adds to voter confusion and cynicism," said Jim Wheaton, head of a coalition of groups pushing another measure -- Proposition 131 -- that calls for public financing of campaigns as well as term limitations. "Our message to politicians is that if you want to get on board this train, we have seats for you, but in the caboose."

"My concern is that Bush's endorsement, coming after Quayle's endorsement and Wilson's endorsement, makes it a partisan issue," said Eddie Mahe, a Washington-based GOP consultant who heads a national group pushing term limits. "That's like handing a gift to Willie Brown," the Democratic Speaker of the California Assembly.

Brown and state Senate president David Roberti (D) have raised an estimated $4 million to defeat both term-limitation measures -- roughly four times the combined sums raised by supporters -- and their efforts are being watched closely all over the country by legislators who hope the term-limitation drive will be derailed in California before it has a chance to sweep into their states.

"This is a very difficult issue for elected officials to try to defuse, because they know their arguments come off as self-serving," noted John Perkins, head of the political action arm of the national AFL-CIO, which quietly invested $35,000 in an unsuccessful effort to defeat a term-limit proposition in Oklahoma last month. "A lot of legislators around the country are rooting for Willie."

If both California propositions pass, virtually all provisions of both would take effect, with the length and nature of the term limits determined by the measure that received the most votes. Prop 140 would impose a lifetime limit of eight years for state senators and statewide officers, and six for Assembly members. Prop 131 would limit legislators to 12 consecutive years and statewide officers to eight consecutive years.

In Colorado, the only other state with a term-limit measure on the ballot next week, no organized opposition has come forward. "Willie Brown is the rare case of a powerful Assembly speaker who has been in office so long, who feels so secure and has so much access to special-interest money that he's willing to mount a fight," said Terry Consodine, leader of Colorado's term-limit drive. "We don't have anything like him here."

The Colorado proposal, unlike the California propositions, would cover federal as well as state offices and is almost certain to be subject to a constitutional challenge if passed.

The Brown- and Roberti-financed television ad campaign against the California term limits began last week. In two of the ads, actresses Angela Lansbury and Sharon Gless brand the term-limit measures as a ploy of politicians to win taxpayer funding for their own campaigns and to give more power to special interests and developers. A third ad, which began airing yesterday, warns that tax dollars could go to finance extremist political groups.

"They're turning the truth on its head," countered Wheaton, who is director of the California Chapter of Common Cause, which has endorsed Prop 131. He noted that the public financing portion of Prop 131 was written in a way that would make it "extremely unlikely" that extremist candidates could qualify.

Lew Uhler, head of the National Tax Limitation Committee and a leading sponsor of Prop 140 -- which does not include public financing of campaigns -- called the ads "outrageous." He noted that by "deliberately confusing" both propositions in the same ad, opponents had adopted a "unite-and-conquer" strategy.

Though Uhler and other supporters are nervous about the drop in the polls and a tad uncomfortable with the endorsements of political leaders, they still believe there is enough grass-roots support for both to pass.

"This isn't an abstract or complex issue," Uhler said. "We spell out very clearly on the ballot that 140, in addition to limiting terms, cuts legislative pensions and staffs and would save taxpayers $70 million. I think voters are going to like that."