California will have an all-Democrat battle this fall for its first open U.S. Senate seat in nearly 25 years.

Attorney General Kamala Harris leads a field of 34 candidates with 39.6 percent of the vote, followed by Orange County Congresswoman Loretta Sanchez with 18 percent. The top Republican, former state party chair Duf Sundheim, trails with 8.7 percent. 

Democratic Attorney General Kamala Harris declared victory before a crowd of supporters in San Francisco around 10 p.m., after the Associated Press projected that she would advance to the November runoff. She stressed a theme of coming together.

"Tonight, California spoke and it said that we are a state that is unified, we are clear in purpose, our unity is our strength and our diversity is our power," Harris says.

The other leading Democrat in the race, Orange County Congresswoman Loretta Sanchez, claimed success as well – hours before the AP projected she would advance. Under California’s open primary system, the top two finishers – regardless of party – move on to the general election.

Sanchez is expected to run as a moderate and appeal to Republicans, and she hinted as much when she spoke to her supporters in Anaheim.

"We are going to win this U.S. Senate seat because we are going up and down the state of California and asking every voter – every place – to come out and vote for us," Sanchez says.

The top Republican finisher, former state party chair Duf Sundheim, acknowledges it’ll be “very difficult” to catch Sanchez but said in an interview late last night that he’s not yet ready to concede.

"We’ve shown that a positive message, that a reformer that is able to work across the aisle and focuses on getting things done can be the leader of the Republican movement in this state," Sundheim says.

Ben Adler's full interview with Duf Sundheim:

Sundheim expressed frustration that there were several other Republicans in the race. The scattered GOP vote allowed two Democrats to advance – marking the first time ever that California voters will send two candidates from the same party to a statewide runoff.