LOS ANGELES -- The Democratic Party has controlled the Legislature for a nearly unbroken stretch of 42 years. Yet control goes only so far: It takes two-thirds of the Legislature to enact a host of important legislation in this state, meaning that even the diminished Republican Party has been able to easily frustrate Democratic ambitions.

But with a swell of electoral victories in November, the Democratic Party has now crossed that boundary and controls two-thirds of both the Senate and the Assembly, giving it the kind of unfettered power that no party has had here for 80 years.

This does not appear to be a passing advantage. Even Republicans say that changes in electoral demographics mean that, with the exception of a few brief lapses caused by vacancies, Democrats could hold a supermajority at least through the end of the decade.

Yet in the "be careful what you wish for" department, Democrats are beginning to confront the struggles and complications that come with being in charge of the store. This authority came at least two years earlier than most Democrats had projected.

And it is unleashing years of pent-up Democratic desires -- to roll back spending cuts, approve a bond issue to rebuild the state's water system, amend the state's tax code, revamp California's governance system -- that had been largely checked by the Republican minority.

At the same time, it is stirring concerns from Democrats, among them Gov. Jerry Brown, that the situation may inspire an overreach that could make the party's reign brief. By contrast, some Democrats argue that handled correctly, the next two years could provide an opportunity to lock in long-term control.

"The center of gravity of the Democratic Party will be restraint, but some people can't help themselves," Brown said in an interview. "The supermajority is not a permanent condition. It's something that can be lost far more easily than it can be gained."

The demand become apparent even before the new Legislature was sworn in this month. State Sen. Ted W. Lieu, a Democrat, proposed reinstating an automobile registration fee that was repealed under Gov. Arnold Schwarzenegger. That fee was a rallying point of what many saw as excessive taxation here; its elimination created a $4 billion revenue shortfall. Lieu pulled back at the urging of Democratic leaders.

"Democrats have unrestricted, unchecked power in the executive and the legislative branch today -- and they have not had that for decades," said James L. Brulte, a former state lawmaker running for state Republican leader. "If you are a Democrat, the good news is that your party is 100 percent in charge of state government. If you're a Democrat, the bad news is that you don't get to blame anybody else if things go wrong. So Democrats own it."

Now that the Democrats have a supermajority, there has been a growing call for lawmakers to put an initiative before voters to revise Proposition 13, either by eliminating the two-thirds requirement or creating a split tax roll, which would protect residential property owners but remove protection from commercial and industrial properties.

"It's Time to Adjust Prop 13," said the headline over a column by George Skelton in The Los Angeles Times on Thursday.