Sacramento -- The state Assembly approved legislation giving significant new rights to domestic partners Wednesday, moving California closer to giving gay couples much of the same legal recognition as married couples.

The vote came after a lengthy debate in which the Legislature's gay and lesbian caucus -- backed by dozens of straight Democratic lawmakers -- delivered passionate pleas for equal rights. Democratic Assemblyman Mark Leno of San Francisco decried his position as "a second-class citizen in this country" moments before the Assembly approved the bill to loud cheers.

"In all candor, I believe that there are some of you who will never accept me and my family for who we are," said Assemblywoman Jackie Goldberg, D-Los Angeles, who spoke of the legal difficulties she and her partner encountered raising their daughter. "I want your acceptance, but I don't need it. I do need equal protection under the law."

The state's 20,000 registered domestic partners would have new powers to raise children, own property together and have a say in how to handle a partner's death under a bill that supporters believe has a good chance of clearing the state Senate and winning the approval of Gov. Gray Davis.

If the bill is enacted, California would provide many of the same rights to domestic partners as Vermont, the only state in the country that recognizes gay marriage.

The measure was approved 41-29, with Republicans arguing that the Democratic-controlled Legislature was overturning a successful 2000 ballot initiative defining marriage as a union between a man and a woman.

"The question is whether we're going to honor the decision of the voters of the state of California or whether we're going to pre-empt them because some members don't feel they made the right choice," said Assemblyman Rick Keene, R- Chico (Butte County).

But supporters noted that federal laws and the California Constitution still prevented gay couples from enjoying more than 1,000 benefits that married couples receive. Domestic partners would have much broader legal recognition under the bill, AB205 by Goldberg.

For example, current law prohibits both partners from having custody rights to a child they are raising. Advocates argue that if a partner dies unexpectedly, the surviving partner has little legal ability to retain custody of the couple's child. That would change under Goldberg's bill.

The bill also would allow gay couples to file state income taxes jointly,

own land together and receive state marital tax exemptions.

The measure also could cost gay couples money: a domestic partner applying for government benefits would have to list a partner's income, thereby reducing his or her entitlement. And couples would be responsible for each other's debts.

Goldberg's bill is considered the most important of several measures being pushed by the five-member gay and lesbian caucus, the first of its kind in any state Legislature.

A bill by Leno to prohibit discrimination against transgender people was approved by the Assembly and is now pending in the Senate. Another measure preventing harassment of foster children based on several factors, including sexual orientation, also has cleared the Assembly.

E-mail Mark Martin at markmartin@sfchronicle.com.