Gov. Gray Davis, campaigning to keep his term from coming to a premature end in the recall election, endorsed a fledgling Democratic proposal last week to dump the planned increase in the car tax in favor of higher taxes on the wealthy and cigarettes.

The swap could help Davis, eliminating a much-despised tax increase that will add an average $160 to the annual fee just a week before the recall election.

But will the unorthodox plan work?

Democratic supporters say the switch requires just a majority vote in the Assembly and Senate -- which means no Republican votes are needed -- because the state's total revenue would not increase under the swap.

The state constitution, however, requires a two-thirds vote for ``any changes in state taxes enacted for the purpose of increasing revenue.''

Opponents say the plan is illegal for two reasons. First, they say the constitutional requirement applies to increases for each individual tax. And second, they point out that the car-tax boost -- which was ``triggered'' in June by the Davis administration without a vote of the Legislature -- represents a $4.2 billion increase in state revenue, so any substitute tax must also be an increase in revenue.

``We think this is nothing more than bait and switch,'' said Assembly Minority Leader Dave Cox, R-Sacramento, who vowed that, if such a bill is passed and signed by Davis, Republicans would challenge it in court. Republicans have also challenged the increase in the car tax, which the Davis administration's finance director concluded could be raised without a legislative vote under a legal provision that trips an increase when state revenues are dire.

Tax experts say state appellate courts have never addressed whether the constitutional provision, which was enacted through Proposition 13, applies each time an individual tax is increased or only when total tax revenues are increased.

The legislative counsel -- who serves as the Legislature's lawyer but whose opinions are not binding -- has supported the Democrats' position in opinions over the past 25 years.

``That language addresses increases in revenues collected from state taxes, rather than increases in revenues from any single tax,'' the then-counsel Bion Gregory wrote in 1981, when asked if the Legislature could pass by majority vote a bill that would apply the sales tax to goods that had been exempt and exempt other goods.

``It's never been challenged before because it's never been done to this grand a scale before,'' said Greg Turner, general counsel for the California Taxpayers' Association, which believes any single tax increase requires a two-thirds vote.

Details of the tax swap being floated by Assemblyman Darrell Steinberg, D-Sacramento, chairman of the Assembly Appropriations Committee, are still being worked out, including exactly which taxes would be raised and by how much.

Davis said Tuesday that swapping out the car tax hike was "a good idea.''

The car tax hike is scheduled to go into effect on new registrations beginning Oct. 1.

``If we can find a legal way to reduce the car tax while raising the taxes that I proposed in my budget in January, I would support it, because I never intended for this burden to fall solely on the motorists of California,'' Davis said.

In addition to the issue of whether it can be done with a majority vote, another major sticking point remains.

Revenue from the car tax -- technically called the ``vehicle license fee'' -- are not subject to Proposition 98, which mandates that 40 percent of all tax revenues go to schools.

The replacement taxes, however, would be subject to Proposition 98. That means a $4.2 billion tax increase on income and cigarettes would net just $2.5 billion for the cities and counties that get the license fee.