Updated

Leading Democrats are uniting with Hollywood producer Steven Bing and hedge fund manager Tom Steyer to oppose a California ballot proposal they fear could hand the 2008 presidential election to the Republican nominee.

A lawyer with ties to the Republican Party wants California voters to change the way the nation's most populous state awards its electoral votes — a proposal Democrats call a power grab but that supporters describe as a blueprint for fairness in presidential contests.

California now allots all of its 55 electoral votes to the statewide winner in presidential elections, a practice followed in most states.

The proposal calls for awarding two electoral votes to the statewide winner, with the rest allocated according to results in each congressional district.

California has voted Democratic in the last four presidential elections. The change — if it qualifies for the June primary ballot and is approved by voters — could mean a Republican could be positioned the following November to win 20 or more electoral votes in GOP-leaning districts.

Nineteen of the state's 53 congressional districts are represented by Republicans. President Bush carried 22 districts in 2004, while losing the statewide vote by double digits.

It takes 270 of 538 electoral votes to win the White House. Only Maine and Nebraska currently allocate their electoral votes by congressional district.

In what is shaping up as an important subplot to the 2008 race, a political committee is being formed by Steyer that will raise money — possibly tens of millions of dollars — to defeat the GOP-backed idea.

The committee is being supported by Sens. Dianne Feinstein and Barbara Boxer, San Francisco Mayor Gavin Newsom, Los Angeles Mayor Antonio Villaraigosa and Democratic leaders in the Legislature.

The proposal is a "power grab orchestrated by the Republicans," Feinstein and Boxer said in a joint statement. It's "another cynical move to keep the presidency in Republican control."

Democrats were scheduled to announce formation of the committee, Californians for Fair Election Reform, on Thursday.

It will be headed by Steyer, who is raising money for Sen. Hillary Rodham Clinton's presidential campaign. A longtime Democratic donor, Steyer also raised funds for John Kerry's 2004 campaign and House Speaker Nancy Pelosi.

"Democrats would lose 20 electoral votes and very likely the presidency if California abandons the winner-take-all system while large Republican states like Florida and Texas do not," Steyer said in a statement.

The Presidential Election Reform Act, as it's dubbed, is being pushed by Thomas Hiltachk, a lawyer in a Sacramento firm that represents the California Republican Party and has worked with Gov. Arnold Schwarzenegger.

"In a state as large and diverse as California, what can be fairer than using congressional districts to apportion electoral votes," said Kevin Eckery, a spokesman for Californians for Equal Representation, a committee backing the proposal.