The race to succeed Sen. Barbara Boxer (D) of California could very well produce the upset of 2016.

The prohibitive favorite would seem to be Kamala Harris. As the state’s two-term attorney general, she has good name recognition and an established political network. As a woman with both African and Asian heritage, she has a unique appeal to the state’s diverse electorate. She has achieved national prominence, albeit in a slightly awkward way. At a San Francisco fundraising event a couple of years ago, President Obama praised her brilliance and toughness, then added: “She also happens to be, by far, the best-looking attorney general in the country.” After getting widespread criticism for the sexist character of this remark, the president apologized. Ms. Harris accepted with good grace.

The GOP has not won a Senate race in the state since 1988, and there is practically no chance that a Republican could outpoll Harris. Carly Fiorina lost to Senator Boxer in 2010, even as Republicans were scoring historic victories in most other states. This election’s GOP Senate candidates are fine men, but have scant funding and visibility. They’d also suffer the additional handicap of running when the Democratic presidential nominee is sure to carry California by a wide margin.

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There is one other significant Democratic candidate: Rep. Loretta Sanchez of Orange County. In contrast to Harris, Representative Sanchez has never run statewide, and her campaign war chest is much smaller. Surveys show her running well behind.

Nevertheless, Sanchez has a serious chance of being California’s next senator. The reason lies in the state’s unusual electoral system. The top two finishers in the June primary, regardless of party, move on to the general election. Although a number of lower-level races have featured same-party opponents in November, it has never happened in a partisan statewide race. It might happen this time. If all the Republican candidates stay on the ballot, they could split the GOP vote, giving the top two slots to Harris and Sanchez.

There are several reasons why Sanchez could win that showdown. First, she stands to be the state’s first-ever Hispanic US senator – a prospect that could gain her support from California’s large and growing Hispanic population. Second, although she is no conservative, her positions are closer to the center than those of the very liberal Harris. If they had to choose between the two, Republicans and conservative-leaning independents would prefer Sanchez. Third, as a member of the Armed Services and Homeland Security Committees in the House, she can claim expertise in national defense and terrorism. Harris has no background in national security, which has become a much bigger issue in the wake of the Paris attacks.

If Harris is no shoo-in, neither is Sanchez. Republicans might unite around one candidate in the primary, keeping Sanchez off the ballot in November. And Sanchez is certainly capable of botching her opportunity. She is more famous for her eccentric political judgments than for her legislative accomplishments. (During the 2000 Democratic convention in Los Angeles, she planned a fundraiser at the Playboy Mansion, and changed the venue only after intense public pressure from party leaders.)

If events align just right for Sanchez, however, the race could be a humdinger that political junkies talk about for years.

Originally published in the Christian Science Monitor.