It's been more than a year since Gov. Arnold Schwarzenegger warned his fellow California Republicans that "we're dying at the box office. We're not filling the seats." But the consequences of the GOP's self-isolating ethnic and ideological narrowness are even more frightening today than they were then. With each passing day, Republicans look ever more like a suicidal cult than a political party.

Conventional wisdom holds that the years of budget gridlock in Sacramento have been the product of the zero-sum conflict between the extreme left of the Democrats and the extreme right of the Republicans -- no cuts in spending on the one side, no increased taxes on the other.

But in the current crisis, the Democrats have in fact agreed to major cuts; the Republicans remain adamant on revenue. That resistance, as most people must know by now, is made possible by California's nearly unique constitutional provision requiring a two-thirds majority in the Legislature to enact a budget or increase taxes. If five Republicans -- two in the state Senate, three in the Assembly, both of which have Democratic majorities -- broke ranks, there'd be no gridlock.

But that's only part of the story. In a survey last year by the Public Policy Institute of California, 52% of the state's Democrats identified themselves as liberals, 31% as "middle of the road" and 17% as conservative.

Republicans were far more rigidly conservative: 67% called themselves conservative, 21% called themselves middle of the road and 8% said they were liberal.

So Democrats are not quite as hard-line as the folklore suggests.

Even more telling: Notwithstanding the passage of the gay marriage ban in November, the reality is that Californians have become increasingly accepting of gay marriage and gay rights in general. So have other Americans -- all except Republicans.

In 1977, according to Mark DiCamillo of the Field Poll, 28% of Californians approved of gay marriage. In 2008, just before the last surge of intensive campaigning led to the narrow passage of Proposition 8, 51% of Californians approved of gay marriage. That reflects a huge increase in tolerance among Democrats (26% to 65%) and independents (33% to 61%) but no change whatever among Republicans (28% to 25%).

Does that mean Republicans are just slow learners? The answer, much more likely, is that a lot of moderate conservatives who a generation ago would have been Republicans (and who might have been more flexible on gay rights) have since become independents or even Democrats.

Membership in both parties has been shrinking as a percentage of the electorate, as the ranks of the independents have been climbing dramatically -- nearly doubling in the last 16 years. But the ranks of Republicans have been declining more rapidly, from 37% of the electorate in 1992 to just over 31% in 2008, a decline of 15%, compared with a decline of 9% among Democrats.

Forty years back, when the party's leaders included such moderates as Bill Bagley, John Veneman and Robert Monagan, California Republicans didn't take no-new-tax pledges, and those who voted for tax hikes didn't face primary opponents backed by their own party.

In 1967, faced with a serious fiscal crisis, Ronald Reagan signed the biggest tax increase in the history of this or any other state.

Similarly, in 1991, Pete Wilson -- facing a huge budget deficit -- negotiated a compromise that more or less split the difference between program cuts and tax increases. Five years ago, Senate Minority Leader Jim Brulte, a smart, fully certified conservative, would say that, despite his conservatism, he was the left wing of his party.

And what applies to ideological narrowness applies as well to gender and ethnicity. Of the 15 Republicans in the state Senate, one is a woman and one is a Latino. Of the 29 GOP Assembly members, one is Vietnamese and four are women. If you don't count the members of Portuguese or Azorean extraction, all the rest are non-Latino white men.

Of the 51 Democrats in the Assembly, 16 are women, 17 are Latinos, six are black and seven are Asian; of the 25 Democrats in the Senate, 12 are women, nine are Latinos and two are black.

In a state where whites have been just another minority for the better part of a decade, and where Latinos will in another generation be an absolute majority, it may not be surprising that that GOP narrowness leads to a gritty sense of besiegement and a kamikaze mentality that seems ready to take itself over the cliff, and the rest of the state with it.

To say that all that is dangerous for both the state and the Republican Party should be obvious. But it's almost as obvious that it's dangerous for the Democrats as well.

Without a strong, engaged opposition, no party in what's essentially a two-party system can remain responsible. In its failure to be fully engaged in the process, the GOP also lets the Democrats, all too eager to please their union and liberal constituents, off the hook. As it is now, every member can either blame the other party or hide behind the blame a sloppy media heap on the generic "Legislature."

The fastest way to restore responsibility all around is to rejoin the rest of the democratic world and bring back straight majority votes to enact budgets and raise taxes. That would break up the GOP cult, make both parties more responsible to the voters as a whole, force them to make the tough choices and take the heat for the consequences, and -- most important -- get on with the business of governing.

Peter Schrag, the former editorial page editor of the Sacramento Bee, is the author, most recently, of "California: America's High-Stakes Experiment."