Democrats had been counting on victories in at least half a dozen California congressional districts to bring them closer to the 24 needed to take control of the U.S. House of Representatives.

Republicans only hold 14 seats in the Golden State, and Hillary Clinton won many of those districts in the 2016 election.

But a combination of factors — including an excess of Democratic contenders, and a surge in Republican enthusiasm — could thwart those plans.

California has a unique primary system called the “top two” or “jungle” primary, under which every voter can vote for any candidates, and the top two vote-winners advance to the general election, regardless of party. That means it is theoretically possible for the general election to feature an all-Democrat — or, less frequently, all-Republican — final.

Until recently, Republicans feared being shut out from the November ballot in statewide races for governor and for U.S. Senate. Now, to their horror, Democrats could fail to make the November ballot in congressional races.

Ben Christopher of Calmatters.org reports:

California Democrats know exactly the trouble they’re in: They have too much of a good thing. Competitive congressional districts across Southern California are packed with qualified, enthusiastic and well-financed candidates touting progressive policies and promising stiff resistance to President Trump’s agenda. The only problem: there are too many of them.

Christopher calls the emerging danger of all-Republican contests in several key races a “nightmare scenario” for the party.

McClatchy also reports:

The political arm of House Democrats is undertaking a late push to drive up voter turnout in a handful of marquee California congressional districts where the party now faces the possibility of not even having a Democrat make it onto the November ballot. … Democrats are concerned that California’s uncommon electoral system — in which the top two vote-getters in a primary advance to the general election regardless of party — will prevent them from winning at least three House seats this fall. The seats – the 39th Congressional District, the 48th Congressional District, and the 49th Congressional District — are each located in the battleground suburbs of Orange County, where a plethora of Democratic candidates in each threatens to split the vote evenly and allow two GOP candidates to move on.

In some races, the party leadership is attempting to persuade voters to unite behind a single primary candidate (which has led to some pushback from the grass roots). In others, the party is simply aiming to boost voter registration and turnout so that there will simply be more votes to divide.

Another reason Democrats are suddenly in trouble is that Republicans are re-engaging in the political process, inspired by a U.S. Department of Justice lawsuit filed in March against California’s “sanctuary state” laws.

That lawsuit inspired local activists, especially in Southern California, to push city and county governments to defy the state’s “sanctuary” laws and to join the federal government’s lawsuit. The White House has stoked the fight by taking on California and Governor Jerry Brown in public.

If Democrats split their vote, and Republicans turn out enthusiastically, California may prove to be the obstacle to Democratic control of the House, rather than the pathway to it.

San Francisco’s own House Minority Leader Nancy Pelosi (D-CA) has vowed to come back as Speaker of the House if Democrats win in November.

Joel B. Pollak is Senior Editor-at-Large at Breitbart News. He was named to Forward’s 50 “most influential” Jews in 2017. He is the co-author of How Trump Won: The Inside Story of a Revolution, which is available from Regnery. Follow him on Twitter at @joelpollak.