Frustrated that presidential candidates have spent so little time in California, lawmakers on Tuesday approved legislation to change how the state awards its electoral votes for president.

The bill would pledge California's 55 Electoral College votes to the winner of the national popular vote, a system critics charged was an attempt to circumvent the U.S. Constitution.

"Presidential candidates would have to come to California because of our population and they would have to take a position on issues that we care about," Assemblyman Tom Umberg, D-Santa Ana, said on the Assembly floor.

The Assembly voted mostly along party lines to approve the bill, 49-31.

The interstate compact they authorized is part of a national campaign launched in February by a Los Altos nonprofit to change the way the nation picks a president. However, if the bill became law in California, it only would take effect if states with a combined total of 270 electoral votes - the number now required to win the presidency - also agreed to decide the election by popular vote.

The Constitution requires each state to select its own Electoral College delegates in presidential races. California currently awards its votes based on the state popular vote, as do most other states.

Backers of the compact say presidential candidates should be forced to campaign before all voters, not just those in so-called battleground states such as Ohio, Michigan, Pennsylvania and Florida.

In 2004, California voters cast more than 10 percent of the nation's votes for president, but presidential or vice-presidential candidates visited the state just twice in the last month of the campaign, according to a committee analysis of the bill.

Republicans called the compact an "end run" around the U.S. Constitution.

"The Constitution of the United States was very specific that every state shall have a republican form of government," said Assemblyman Chuck Devore, R-Irvine. "It's not a direct democracy. Direct democracies were probably seen by the founding fathers as unstable."

Instead, Devore said California should consider apportioning its electoral votes by congressional district, an approach the Assembly has previously rejected as a partisan move to split California's votes.

A compact agreement would require California to give its electoral votes to the winner of the national vote regardless of which presidential candidate state voters select.

Critics said a popular vote system would send presidential candidates only to the most populous cities, shutting out rural America.

"I don't want a candidate to go to 10 to 12 big urban centers and walk away with the presidency," said Assemblyman Mike Villines, R-Fresno.

Republican Gov. Arnold Schwarzenegger has not taken a position on the bill, spokesman Darrel Ng said.

Democrats said the votes shouldn't fall along party lines. A committee analysis shows Kerry would have won the presidency in 2004 if he had garnered 60,000 more votes in Ohio, even though President Bush won 2.8 million more votes nationwide. Under the compact, California's electoral college votes would have gone to Bush in that case, they said.

Barry Fadem, an attorney with the National Popular Vote campaign, said the group hopes to find lawmakers to carry their bill in each state by the end of the year.

"People really care about how we elect the president of the United States," Fadem said.

The Colorado Senate in April voted to ratify the compact. The proposal also is being considered in four other states - New York, Louisiana, Illinois and Missouri.

The bill is AB 2948.