A proposal to split the nation’s most populous state into three smaller states would give Democrats a huge boost in the perpetual battle for control of the United States Senate — likely dooming the plan even before voters have a chance to weigh in.

California voters will vote this November on the ballot measure, backed by tech billionaire and venture capitalist Tim Draper. If the measure passes, Congress would have a year to allow the state to split up into three separate states — one centered around Los Angeles, another in Northern California that includes the Bay Area and Sacramento, and a third in Southern California that would include the Central Valley and San Diego.

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Democrats have easily won California’s electoral votes in recent years. George H.W. Bush was the last Republican to win the state at the presidential level, and Republicans haven’t won a Senate seat in California since Pete Wilson won reelection in 1988.

But if Democrats are leery of splitting California’s 55 electoral votes, recent election results show the three new states all would have voted for Democratic presidential nominees Hillary Clinton Hillary Diane Rodham ClintonDemocratic groups using Bloomberg money to launch M in Spanish language ads in Florida The Hill's Campaign Report: Presidential polls tighten weeks out from Election Day More than 50 Latino faith leaders endorse Biden MORE in 2016 and Barack Obama Barack Hussein ObamaThe Memo: Trump's strengths complicate election picture Obama shares phone number to find out how Americans are planning to vote Democrats' troubling adventure in a 'Wonderland' without 'rule of law' MORE in 2008 and 2012.

Data compiled by Ballotpedia, the political analysis firm, found Clinton would have won more than 60 percent of the vote in both California — the Los Angeles-based state — and Northern California. She would have won almost 52 percent of the vote in Southern California, while President Trump Donald John TrumpBiden on Trump's refusal to commit to peaceful transfer of power: 'What country are we in?' Romney: 'Unthinkable and unacceptable' to not commit to peaceful transition of power Two Louisville police officers shot amid Breonna Taylor grand jury protests MORE would have taken 42 percent.

Obama would have won all three states in 2012 and 2008, though he would have won the San Diego-based Southern California state by just 27,000 votes over Mitt Romney Willard (Mitt) Mitt RomneyBiden on Trump's refusal to commit to peaceful transfer of power: 'What country are we in?' Romney: 'Unthinkable and unacceptable' to not commit to peaceful transition of power The Memo: Trump's strengths complicate election picture MORE in 2012, a margin of just six-tenths of a percentage point.

That means Democrats would have earned 59 electoral votes — four more than they did in 2016, because every state gets two more electoral votes than the number of representatives it sends to Congress — though a third of those votes would have been far more competitive than they are at present.

“All three of them have voted for Democratic candidates the past three presidential elections. Southern California, however, has been much more competitive,” said Ryan Byrne, a Ballotpedia analyst who crunched the data.

Registered Democrats would outnumber Republicans in all three states, according to data from the California secretary of state’s office. The margin is closest in Southern California, where Democrats would enjoy about a 200,000-voter advantage.

The certain benefit for Democrats would be in the battle for control of the U.S. Senate. The heavily Democratic tilt of both the Los Angeles-based and San Francisco-based states would almost certainly mean at least four Senate seats would be firmly in Democratic control, and the other two would be competitive.

Carving up the state would be such a gamble for both parties that the plan would face serious hurdles in Congress, Byrne said. Both parties have something significant to lose, which means both parties have an incentive to oppose changing the status quo.

“Would the US Congress approve this? That’s the part there’s a lot more doubt around,” he said. “For the Democrats, there’s the potential for losing electoral votes. For Republicans, there’s likely at least two more Senate seats, and two more that would be competitive.”

Draper, who earlier pushed to split California into six states, says California is so big it has become ungovernable and that three separate states would become more manageable.

But it’s not even clear if Draper’s measure would pass muster with the courts. Only state legislatures can petition Congress to create new states. And while the ballot measure purports to act as a proxy for the legislature, it would almost certainly be challenged if it were to pass in November.

The state Legislative Analyst’s Office said the legislature might still have to sign off on the plan before it goes to Congress, even if voters approve the initiative.

History is not kind to efforts to divide California, or any other state. Since becoming a state in 1850, there have been more than 200 petitions, movements or legislative efforts to split California. Northern rural counties have tried to carve-out a conservative bastion. Southern counties have tried to make a home for themselves.

The legislature actually passed, and Gov. John Weller signed, a measure in 1859 to create a new Territory of Colorado. But as the Civil War loomed, Congress never took up the proposal.

And some liberals even want the entire state to separate itself from the United States. Supporters of a so-called Calexit campaign gathered more than half a million signatures to qualify for November’s ballot.

The last time any state split itself in two came in 1863, when rural counties that backed the Union took West Virginia out of Virginia.