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Democrats are far-and-away favored to keep Sen. Barbara Boxer's California Senate seat when she retires in 2016. They may even be able to shut Republicans out of the general election altogether. But, with both parties still feeling their way through recent and radical changes to the state's rules for primary races, Democratic insiders see a nightmare scenario in which they fumble away the seat before the general election even begins.

At issue are California's new "top-two" (or "jungle") primaries, which have replaced party primaries with an open primary race in which the top two vote recipients—regardless of party affiliation—face off in a general election. The thinking behind the new system was to keep races competitive even in places that were traditionally "safe" areas for one party. But it also creates a scenario in which both parties face the prospect of being without a candidate in high-profile, statewide elections.

With Democrats making up 43 percent of the state's electorate in 2014 and Republicans only 28 percent, the GOP appears the more likely party to miss out on the general, and the party is steeling for the possibility. "I would hate to see a situation in California where we end up with two Democrats running against each other for the U.S. Senate seat" in the general election, said Harmeet Dhillon, the vice chairwoman of the state Republican Party. "But it's a real possibility with the top-two system."

Democrats, however, are nervously aware of a nightmare scenario of their own, in which a wealth of strong Democratic candidates divides the party faithful and leaves two Republicans alone at the top.

"The danger of top-two is getting boxed out," said Ben Tulchin, a San Francisco-based Democratic pollster. "Say you have two Republicans fairly evenly matched, and then a large and diverse field of Democrats splitting the vote—say four or more Democrats ... with different factions of the Democratic vote."

It was a scenario nobody thought would happen, until it did: California's 31st District—a Southern California seat that should have been a straightforward win for Democrats—went to the GOP in 2012 after a large group of Democrats split the vote and left two Republicans as the top primary vote-getters. (The seat eventually went to Republican Gary Miller, who retired rather than risking defeat in 2014.)

The same scenario replayed in the Senate, with its six-year terms, would be an exponentially bigger disaster for Democrats.

And a crowded field of Democrats started forming soon after Boxer announced her retirement last week. State Attorney General Kamala Harris, who announced Tuesday that she would seek the seat, has attracted the most attention. The former San Francisco district attorney has the inside track on the state's most reliable source of Democratic votes and would be a favorite in the general election. The other rising, Bay Area-based Democratic star, Lt. Gov. Gavin Newsom, said the day before that he would not run.

But there are plenty of others still looking. From Northern California, young Democratic Rep. Eric Swalwell—who defeated an incumbent in a Democrat-versus-Democrat general election in 2012—is considering a Senate run after two terms in the House, according to his consultant Lisa Tucker. ("He's had several supporters call and ask him to consider it," Tucker said.)

In Southern California, Rep. Loretta Sanchez announced Tuesday that she's "seriously considering" running. She and former Los Angeles Mayor Antonio Villaraigosa, who's also considering a campaign, could attract significant Hispanic and L.A.-area support. Another statewide official also from Southern California, Treasurer John Chiang, might be able to tap into the state's growing Asian population if he ran. And Bay Area billionaire Tom Steyer, another possible candidate, has clout on the key issue of climate change and other environmental concerns that are of importance to Democratic voters.

Republicans acknowledge they have almost no shot to win a Senate race in a state like California, but they see the Democrats-cancel-each-other-out scenario as their best hope.

Among Republicans, Fresno Mayor Ashley Swearengin—who lost her 2014 race for state controller by only eight percentage points—would be an appealing candidate, while San Diego-area Assemblyman Rocky Chavez told his local paper he's been approached about running and former California Republican Party chairs Tom Del Beccaro and Duf Sundheim are also in the mix. However, Dhillon said she thought experience in elected office, which the former GOP officials don't have, might be a prerequisite for seeking the seat.

"The ideal outcome for Republicans is two candidates with incredibly high name ID, as high as you can get, maybe one from Northern California and one from Southern California, and then every Democrat on the planet adds their name to the ballot," said Matt Rexroad, a Republican consultant and county supervisor. For Democrats, he said, "it's going to be a difficult task exercising discipline within the party when people actually think they can be the replacement for Barbara Boxer," while Republicans could face issues finding candidates interested in such a long-shot effort.

With this being the first open Senate race in the state since 1992, it will be difficult for Democrats to convince candidates to take one for the party and stay out. "I really think, though, that so many Democrats are tired of waiting that a lot of them will jump in and run," Dhillon said.

It's a perfect storm-like scenario, to be sure, but not one that Democrats think of as impossible.

"We're Democrats!" Tulchin laughed. "But I would like to think that with what would be at stake here with a U.S. Senate seat, not just a California race but a national race with control of Congress at stake, that there would be enough impact and influence from donors and the party to keep something like that from happening."

"You have to prepare for the worst because crazy stuff can happen," he said. "They call it a jungle primary because it is kind of crazy and everyone's fending for themselves."

This article is from the archive of our partner National Journal.

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