But Kermit Roosevelt, a constitutional law professor at the University of Pennsylvania, says a California secession would never happen because it’s not in the best interest of the United States.

“There is no way this will happen,” Roosevelt said. “I’m not surprised people are talking about it. If the election had gone differently, it would be Texas trying to do this. But it’s not realistic.”

Roosevelt said there is currently no legal framework allowing states to secede. Creating the framework would require an amendment to the U.S. Constitution. An amendment can be proposed with two-thirds approval from both houses of Congress or at a constitutional convention, called for by two-thirds of state legislatures. That amendment would then have to be ratified by three-fourths of state legislatures.

“What state would be next?” Roosevelt said. “One of the reasons we wanted one country was that America would be better on the global scale if we weren’t fragmented like Europe.”

California is not alone in fantasizing about life without federal rule. In Oregon on Friday, two people submitted a ballot proposal for that state’s secession from the union.

Marcus Ruiz Evans, a spokesman for Yes California, says his organization has plans laid out — and knows what it’s up against. Sure, the idea of seceding “is almost impossible, but that doesn’t mean it couldn’t happen,” Evans said.

The odds may be similar to what some pegged Trump’s chances of winning the presidency were last year when the political outsider announced his intention to run, supporters said.

But Evans said the first step isn’t to gauge whether seceding is feasible. He said first they must find out whether Californians want to go it alone.

“You can’t even have these questions on constitutionality and whether America will allow it until we establish California wants it,” Evans said. “You have to have a vote.”

The group lists nine points — on issues including education, immigration, trade, regulation and the environment — for why it believes California, which it says has the sixth-largest economy in the world, would be better off as its own nation. It argues California loses money by subsidizing other states and then has to raise state taxes to improve its own infrastructure, schools and colleges. The group also says California’s culture and values set the state apart from the rest of the country.

Yes California is raising money to fund signature gathering for a ballot measure in 2018 that would call for a special election in 2019 in which voters in the state could decide if they want to secede.

“We’re telling protesters, ‘When you are done being upset, if you want to be part of something to fix it, we are here,’” Evans said.

Some Trump supporters, including conservative radio host Bill Mitchell, welcomed California’s departure, saying on Twitter that “#Calexit isn’t a bad idea. Send all the illegals there and the rest of us never have another Democrat President.”

The secessionist effort joins other movements to redraw California’s map. Some rural Northern California residents, along with parts of southern Oregon, have been fighting for years to carve out a new independent State of Jefferson. And Silicon Valley venture capitalist Tim Draper put $5 million into a failed proposal to divide California into six separate states.

But Silicon Valley’s response to #Calexit is hardly uniform.

“I think it’s the absolute wrong reaction,” said Venky Ganesan, managing director at Menlo Ventures. “When you have trouble in your marriage, you don’t call your divorce attorney. You call a therapist first.”

Melody Gutierrez and Jessica Floum are San Francisco Chronicle staff writers. Email: [email protected], [email protected] Twitter: @MelodyGutierrez, @jfloum