California's U.S. Senate contest turned into a dominant win for state Attorney General Kamala Harris over her opponent, Orange County Congresswoman Loretta Sanchez. 

The Associated Press projected a win for Harris after the first round of early returns had her holding a two to one advantage over her opponent. The wide gap was not a surprise; Harris has consistently led in political polls by double digits as Sanchez trailed behind. 

"This is about California. This is about who we are. We are California. We are proud," Harris said, addressing a cheering crowd at her election night returns party in downtown Los Angeles Tuesday night.

With her victory, Harris will be the first biracial woman elected to the Senate. Harris is African-American and South Asian-American. Sanchez would have been the first Latina senator.

Harris will succeed outgoing U.S. Sen. Barbara Boxer, who is retiring. During Harris' opening remarks she talked about the uncertainty of the presidential election and how she plans to uphold California's ideals.

"I intend to fight for a state that has the largest number of immigrants documented and undocumented of any state in this country and do everything we can to bring them justice and dignity and fairness under the law and pass comprehensive immigration reform," Harris said. 

The open seat was rare for California’s Senate delegation and the race to fill it was historic in key ways.

For one, the contest represents the largest test so far of the state’s top-two system in which the two candidates with the most votes in the primary election move on to the general election, regardless of political party.

The process placed the two Democrats on the ballot for the Senate seat and split traditional party alliances. 

Sanchez told supporters gathered at an election night returns party in Santa Ana that she had entered the race after some advised her not to. But she said she wanted to give California voters a choice.

"I'm a fighter and I have no regrets," she said. "Even if we don't make it over the line tonight, never underestimate Loretta Sanchez."

Several dozen volunteers attended Sanchez's event. Though many chairs remained empty throughout the night, the congresswoman was greeted with warm applause shortly when she arrived. 

A 21-year-old Fullerton resident, Krista Abasi, let out a sigh when she learned that Harris was projected to win the seat. Abasi said the news was disappointing and that she preferred Sanchez' tone and style.

"She's very passionate about what she says and she really wants the best for her constituents," Abasi said.

Harris was the early favorite of the state Democratic Party, which endorsed her over her rival -- this despite Sanchez' 19 years in Congress.

President Obama also backed Harris over Sanchez and appeared in a TV ad for her, and former New York Mayor Michael Bloomberg held a fundraiser for Harris in August.

Without the traditional backing from her own party, Sanchez made a pitch for Republican support. She emphasized her national security credentials as a member of the House Armed Services Committee and the House Homeland Security Committee. But there was little evidence that the effort worked.

Few issues divided Harris and Sanchez. For example, both support immigration reform with a pathway to citizenship, climate change legislation, and free or low community college tuition. 

If they parted company, it was in their differing styles. Harris appeared polished and reserved in comparison to Sanchez, whose off-the-cuff comments sometimes got her into political trouble.

In one unguarded moment, Sanchez once made a whooping cry in reference to Native Americans during an apparent joke. She later apologized. Comments about Muslims and her contention that some would engage in terrorism also drew fire.

Republicans were particularly disengaged when it came to the Senate race, there being no GOP candidate to back. More than half of Republicans said they planned not to vote or were undecided about how they would vote, said Mark Baldassare, Public Policy Institute of California president and chief executive officer.

This story has been updated.

Mary Plummer